Stroke biomarkers provide much insight into stroke biology that could be translated for patient benefit. When carefully harnessed, these biomarkers could guide decision-making in challenging clinical scenarios. This article offers an overview on current notable brain biomarkers that could aid clinicians in acute stroke management.
by Geelyn J.L. Ng and Dr Raymond C.S. Seet
Introduction
Stroke is a leading cause of permanent disability and the second most important cause of death globally [1]. Against a backdrop of a rapidly ageing society, there are concerns that a silent epidemic of stroke looms over our population.
Ischemic stroke, a subset that affects 87% of stroke population, results from atherosclerosis that affects predominantly the cerebral vasculature. Atherosclerosis of the blood vessels can lead to a cessation or depletion of blood flow to the brain, triggering cerebral ischemia when brain tissues are no longer viable. Blood clots can also be formed in blood vessels and in the heart, subsequently dislodging into the brain (‘embolic stroke’). Presently, there are only two clinically adopted methods of acute reperfusion treatment – intravenous recombinant tissue plasminogen activator (TPA) [2] and endovascular treatment through device-driven retrieval or aspiration of blood clots [3]. Although good functional recovery is five times more likely to occur with early reperfusion [3], the use of acute reperfusion treatment is restricted to a small group of patients where the benefits of treatment are weighed against the persisting risk of hemorrhagic transformation [4].
Sieving out stroke patients who are at risk of recurrent attacks is the first step to enable accurate triaging of patients to specialized units for in-depth observation and individualized treatment for complications arising from stroke. Presently, such identification is highly reliant on a clinician’s intuition and knowledge of neurologic deficits, as well as neuroimaging results. Tapping into the use of cerebral ischemia biomarkers could shed light on the complex pathological consequences following ischemic stroke and bring forth an unbiased system to weigh risks and benefits of treatments for clinicians and researchers alike.
Biomarkers are biological indicators of physiology that are objectively measured for use in risk stratification and development of therapeutic strategies. Having high sensitivity and specificity for the outcome it is expected to diagnose is generally a trait of a good biomarker, especially when targeting a complex and heterogenous disease such as stroke. Using a multi-biomarker platform could aim at different pathways of this multifaceted disease, thereby allowing for a more comprehensive treatment. Due to the presence of the blood-brain barrier (BBB) that holds a tight control over the inflow and outflow of particles, human brain tissues are typically difficult to access, making it impracticable to measure a biomarker within the brain. During cerebral ischemia, the BBB is broken down, causing brain-derived biomarkers to be released into the blood circulation, making it possible for a closer examination of the pathologic processes that take place following stroke onset. Although many biomarkers exist that could aid in stroke research, we have previously focused on notable blood-based stroke biomarkers that may play a bigger part in supporting the difficult clinical decision-making process [5]. This article will be providing an overview of several well-researched blood-based biomarkers, with much potential in aiding the clinical assessment of stroke patients.
Stroke biomarkers in the clinical scene
Studies in ischemic stroke have investigated the usefulness of blood-based biomarkers in identifying stroke mimics, establishing stroke etiology and prognosticating stroke severity and outcomes, such as vascular events and functional recovery [6, 7]. Presently, use of biomarkers in routine clinical practice remains uncommon, as stroke severity is still determined mainly through a thorough clinical neurological assessment and subjective interpretation of neuroimaging findings by a skilled physician. Nevertheless, having an objective means to prognosticate an outcome via a blood sample retrieved from a patient upon stroke presentation could add value to clinical decision-making, especially during times when neuroimaging results and clinical interpretations are unable to yield conclusive results. As stroke is a heterogeneous condition, investigating biomarkers that target different stroke pathways could be promising in establishing a multi-biomarker platform, especially for outcomes such as hemorrhagic transformation (HT), early neurologic deterioration (END) and malignant cerebral infarction.
Matrix metalloproteinase-9
Although administrating TPA could potentially achieve the benefit of arterial recanalization, the risk of symptomatic intracranial secondary hemorrhage within the infarcted brain tissues must not be forgotten. Matrix metalloproteinase-9 (MMP-9) is an enzyme that degrades the basal lamina and breaks down the extracellular matrix when activated during TPA treatment. The function of the BBB is crippled in this process and an inflammatory cascade is initiated, resulting in edema and the dreaded HT [8]. Apart from its involvement in HT, MMP-9 could also be used to identify high-risk END patients and plays a part in malignant cerebral infarction.
C-reactive protein
C-reactive protein (CRP) is a sensitive systemic marker of inflammation and a well-researched biomarker of ischemic stroke found in the blood plasma. CRP has been associated with END and noted to be predictive of adverse outcome, where ischemic stroke patients with higher CRP levels tend to suffer from a significantly worse outcome and mortality [9, 10].
S100β
S100β is a biomarker of ischemic stroke expressed by neuronal cells that can be released into the bloodstream when the BBB is compromised. Its concentration needs to be carefully balanced, as it may be protective in low concentrations, but at high levels has been shown to predict cerebral malignant infarction and correlate with infarct size [11, 12]. However, trial data on the use of biomarkers to guide clinical decisions leading to early decompressive surgery are currently lacking. Several studies have also uncovered an increase in S100β in ischemic stroke patients who present 1 to 7 days from symptom onset [13, 14]. In acute stroke patients, elevated S100β serum levels before thrombolytic therapy have also been demonstrated as a risk factor for HT [15].
N-terminal pro-brain natriuretic peptide
The brain natriuretic peptide (BNP) and its precursor, N-terminal proBNP (NT-proBNP), have been extensively studied as useful biomarkers for the prognosis and diagnosis of heart failure [16]. In recent years, BNP is gradually gaining recognition as a marker of atrial fibrillation (AF) and, therefore, as a biomarker to diagnose and predict stroke of cardioembolic origin [17, 18]. Plasma BNP levels have also been demonstrated to have significant correlations with infarct volume and National Institutes of Health stroke scale (NIHSS), making it a potentially powerful clinical biomarker for acute ischemic stroke [19].
Uric acid
Although uric acid has been adopted clinically for metabolic diseases, it is slowly garnering interest in the field of cardiovascular diseases due to its antioxidant properties. Despite data to suggest a strong association between uric acid levels and positive stroke outcomes [20, 21], several studies have observed an adverse relationship where higher uric acid levels were found to predict poor functional outcome and increased mortality [22, 23]. This disparity could highlight a dual role of uric acid in stroke, where both high and low levels of uric acid could adversely affect stroke outcomes [24]. Much remains to be explored for this biomarker before it could be roled out for use in stroke prognosis or diagnosis.
F2-isoprostanes
The product of arachidonic acid peroxidation generated by free radicals, F2-isoprostanes is well-established as a reliable biomarker for oxidative damage. Even though stroke is widely known as partly the result of oxidative damage, the relationship between F2-isoprostanes and human stroke remains poorly understood. Studies have demonstrated its importance in ischemic stroke as elevated levels of F2-isoprostanes could be observed in patients during the early course of stroke onset, with one even as early as three hours after [25–27].
Conclusion
Cerebral ischemia biomarkers have the potential to bridge translational gaps in medicine by shedding light on the pathological events leading to cerebral infarction and the ischemic cascade, aiding in clinical assessment during the critical time-sensitive decision-making process. Results in this area are still emerging, and more efforts could focus on ensuring the feasibility of incorporating stroke biomarkers for patient benefit. The translation of stroke biomarkers to clinical practice is challenging but can be extremely rewarding, especially when such concerted efforts of researchers, clinicians, industry partners and regulatory authorities result in a positive outcome for stroke patients.
Acknowledgements
We would like to thank the National Medical Research Council, Singapore (NMRC/CSA-SI/0003/2015, NMRC/CNIG/1115/2014 and NMRC/MOHIAFCat1/0015/2014) for their generous support.
References
1. GBD 2015 Mortality and Causes of Death Collaborators. Global, regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980-2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet 2016; 388(10053): 1459–1544.
2. NINDS rt-PA Stroke Study Group. Tissue plasminogen activator for acute ischemic stroke. N Engl J Med 1995; 333(24): 1581–1587.
3. Powers WJ, Derdeyn CP, Biller J, Coffey CS, Hoh BL, Jauch EC, et al. 2015 American Heart Association/American Stroke Association focused update of the 2013 guidelines for the early management of patients with acute ischemic stroke regarding endovascular treatment: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke 2015; 46(10): 3020–3035.
4. Seet RC, Rabinstein AA. Symptomatic intracranial hemorrhage following intravenous thrombolysis for acute ischemic stroke: a critical review of case definitions. Cerebrovasc Dis 2012; 34(2): 106–114.
5. Ng GJL, Quek AML, Cheung C, Arumugam TV, Seet RCS. Stroke biomarkers in clinical practice: a critical appraisal. Neurochem Int 2017; 107: 11–22.
6. Bustamante A, López-Cancio E, Pich S, Penalba A, Giralt D, García-Berrocoso T, et al. Blood biomarkers for the early diagnosis of stroke: The Stroke-Chip Study. Stroke 2017; 48(9): 2419–2425.
7. Whiteley W, Chong WL, Sengupta A, Sandercock P. Blood markers for the prognosis of ischemic stroke: a systematic review. Stroke 2009; 40(5): e380–389.
8. Barr TL, Latour LL, Lee KY, Schaewe TJ, Luby M, Chang GS, et al. Blood-brain barrier disruption in humans is independently associated with increased matrix metalloproteinase-9. Stroke 2010; 41(3): e123–128.
9. Muir KW, Weir CJ, Alwan W, Squire IB, Lees KR. C-reactive protein and outcome after ischemic stroke. Stroke 1999; 30(5): 981–985.
10. Idicula TT, Brogger J, Naess H, Waje-Andreassen U, Thomassen L. Admission C-reactive protein after acute ischemic stroke is associated with stroke severity and mortality: the ‘Bergen stroke study’. BMC Neurol 2009; 9: 18.
11. Vahedi K, Hofmeijer J, Juettler E, Vicaut E, George B, Algra A, et al. Early decompressive surgery in malignant infarction of the middle cerebral artery: a pooled analysis of three randomised controlled trials. Lancet Neurol 2007; 6(3): 215–222.
12. Abraha HD, Butterworth RJ, Bath PM, Wassif WS, Garthwaite J, Sherwood RA. Serum S-100 protein, relationship to clinical outcome in acute stroke. Ann Clin Biochem 1997; 34(Pt4): 366–370.
13. Aurell A, Rosengren LE, Karlsson B, Olsson JE, Zbornikova V, Haglid KG. Determination of S-100 and glial fibrillary acidic protein concentrations in cerebrospinal fluid after brain infarction. Stroke 1991; 22(10): 1254–1258.
14. Buttner T, Weyers S, Postert T, Sprengelmeyer R, Kuhn W. S-100 protein: serum marker of focal brain damage after ischemic territorial MCA infarction. Stroke 1997; 28(10): 1961–1965.
15. Foerch C, Wunderlich MT, Dvorak F, Humpich M, Kahles T, Goertler M, et al. Elevated serum S100B levels indicate a higher risk of hemorrhagic transformation after thrombolytic therapy in acute stroke. Stroke 2007; 38(9): 2491–2495.
16. Yancy CW, Jessup M, Bozkurt B, Butler J, Casey DE, Drazner MH, et al. 2013 ACCF/AHA Guideline for the management of heart failure: A report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines. Circulation 2013; 128(16): e240–327.
17. Naya T, Yukiiri K, Hosomi N, Takahashi T, Ohkita H, Mukai M, et al. Brain natriuretic peptide as a surrogate marker for cardioembolic stroke with paroxysmal atrial fibrillation. Cerebrovasc Dis 2008; 26(4): 434–440.
18. Fonseca AC, Matias JS, Pinho e Melo T, Falcao F, Canhao P, Ferro JM. N-terminal probrain natriuretic peptide as a biomarker of cardioembolic stroke. Int J Stroke 2011; 6(5): 398–403.
19. Tomita H, Metoki N, Saitoh G, Ashitate T, Echizen T, Katoh C, et al. Elevated plasma brain natriuretic peptide levels independent of heart disease in acute ischemic stroke: correlation with stroke severity. Hypertens Res 2008; 31(9): 1695–1702.
20. Amaro S, Urra X, Gomez-Choco M, Obach V, Cervera A, Vargas M, et al. Uric acid levels are relevant in patients with stroke treated with thrombolysis. Stroke 2011; 42(1 Suppl): S28–32.
21. Chamorro A, Obach V, Cervera A, Revilla M, Deulofeu R, Aponte JH. Prognostic significance of uric acid serum concentration in patients with acute ischemic stroke. Stroke 2002; 33(4): 1048–1052.
22. Weir CJ, Muir SW, Walters MR, Lees KR. Serum urate as an independent predictor of poor outcome and future vascular events after acute stroke. Stroke 2003; 34(8): 1951–1956.
23. Karagiannis A, Mikhailidis DP, Tziomalos K, Sileli M, Savvatianos S, Kakafika A, et al. Serum uric acid as an independent predictor of early death after acute stroke. Circ J 2007; 71(7): 1120–1127.
24. Seet RC, Kasiman K, Gruber J, Tang SY, Wong MC, Chang HM, et al. Is uric acid protective or deleterious in acute ischemic stroke? A prospective cohort study. Atherosclerosis 2010; 209(1): 215–219.
25. Sanchez-Moreno C, Dashe JF, Scott T, Thaler D, Folstein MF, Martin A. Decreased levels of plasma vitamin C and increased concentrations of inflammatory and oxidative stress markers after stroke. Stroke 2004; 35(1): 163–168.
26. Ward NC, Croft KD, Blacker D, Hankey GJ, Barden A, Mori TA, et al. Cytochrome P450 metabolites of arachidonic acid are elevated in stroke patients compared with healthy controls. Clin Sci (Lond) 2011; 121(11): 501–507.
27. Seet RC, Lee CY, Chan BP, Sharma VK, Teoh HL, Venketasubramanian N, et al. Oxidative damage in ischemic stroke revealed using multiple biomarkers. Stroke 2011; 42(8): 2326–2329.
The authors
Geelyn J.L. Ng1,2 BSc, Raymond C.S. Seet*1,2 MBBS, MRCP (UK), MMed (Int Med), FRCP (UK)
1Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
2Division of Neurology, Department of Medicine, National
University Health System, Singapore
*Corresponding author
E-mail: raymond_seet@nuhs.edu.sg
Translating stroke biomarkers for patient benefit
, /in Featured Articles /by 3wmediaStroke biomarkers provide much insight into stroke biology that could be translated for patient benefit. When carefully harnessed, these biomarkers could guide decision-making in challenging clinical scenarios. This article offers an overview on current notable brain biomarkers that could aid clinicians in acute stroke management.
by Geelyn J.L. Ng and Dr Raymond C.S. Seet
Introduction
Stroke is a leading cause of permanent disability and the second most important cause of death globally [1]. Against a backdrop of a rapidly ageing society, there are concerns that a silent epidemic of stroke looms over our population.
Ischemic stroke, a subset that affects 87% of stroke population, results from atherosclerosis that affects predominantly the cerebral vasculature. Atherosclerosis of the blood vessels can lead to a cessation or depletion of blood flow to the brain, triggering cerebral ischemia when brain tissues are no longer viable. Blood clots can also be formed in blood vessels and in the heart, subsequently dislodging into the brain (‘embolic stroke’). Presently, there are only two clinically adopted methods of acute reperfusion treatment – intravenous recombinant tissue plasminogen activator (TPA) [2] and endovascular treatment through device-driven retrieval or aspiration of blood clots [3]. Although good functional recovery is five times more likely to occur with early reperfusion [3], the use of acute reperfusion treatment is restricted to a small group of patients where the benefits of treatment are weighed against the persisting risk of hemorrhagic transformation [4].
Sieving out stroke patients who are at risk of recurrent attacks is the first step to enable accurate triaging of patients to specialized units for in-depth observation and individualized treatment for complications arising from stroke. Presently, such identification is highly reliant on a clinician’s intuition and knowledge of neurologic deficits, as well as neuroimaging results. Tapping into the use of cerebral ischemia biomarkers could shed light on the complex pathological consequences following ischemic stroke and bring forth an unbiased system to weigh risks and benefits of treatments for clinicians and researchers alike.
Biomarkers are biological indicators of physiology that are objectively measured for use in risk stratification and development of therapeutic strategies. Having high sensitivity and specificity for the outcome it is expected to diagnose is generally a trait of a good biomarker, especially when targeting a complex and heterogenous disease such as stroke. Using a multi-biomarker platform could aim at different pathways of this multifaceted disease, thereby allowing for a more comprehensive treatment. Due to the presence of the blood-brain barrier (BBB) that holds a tight control over the inflow and outflow of particles, human brain tissues are typically difficult to access, making it impracticable to measure a biomarker within the brain. During cerebral ischemia, the BBB is broken down, causing brain-derived biomarkers to be released into the blood circulation, making it possible for a closer examination of the pathologic processes that take place following stroke onset. Although many biomarkers exist that could aid in stroke research, we have previously focused on notable blood-based stroke biomarkers that may play a bigger part in supporting the difficult clinical decision-making process [5]. This article will be providing an overview of several well-researched blood-based biomarkers, with much potential in aiding the clinical assessment of stroke patients.
Stroke biomarkers in the clinical scene
Studies in ischemic stroke have investigated the usefulness of blood-based biomarkers in identifying stroke mimics, establishing stroke etiology and prognosticating stroke severity and outcomes, such as vascular events and functional recovery [6, 7]. Presently, use of biomarkers in routine clinical practice remains uncommon, as stroke severity is still determined mainly through a thorough clinical neurological assessment and subjective interpretation of neuroimaging findings by a skilled physician. Nevertheless, having an objective means to prognosticate an outcome via a blood sample retrieved from a patient upon stroke presentation could add value to clinical decision-making, especially during times when neuroimaging results and clinical interpretations are unable to yield conclusive results. As stroke is a heterogeneous condition, investigating biomarkers that target different stroke pathways could be promising in establishing a multi-biomarker platform, especially for outcomes such as hemorrhagic transformation (HT), early neurologic deterioration (END) and malignant cerebral infarction.
Matrix metalloproteinase-9
Although administrating TPA could potentially achieve the benefit of arterial recanalization, the risk of symptomatic intracranial secondary hemorrhage within the infarcted brain tissues must not be forgotten. Matrix metalloproteinase-9 (MMP-9) is an enzyme that degrades the basal lamina and breaks down the extracellular matrix when activated during TPA treatment. The function of the BBB is crippled in this process and an inflammatory cascade is initiated, resulting in edema and the dreaded HT [8]. Apart from its involvement in HT, MMP-9 could also be used to identify high-risk END patients and plays a part in malignant cerebral infarction.
C-reactive protein
C-reactive protein (CRP) is a sensitive systemic marker of inflammation and a well-researched biomarker of ischemic stroke found in the blood plasma. CRP has been associated with END and noted to be predictive of adverse outcome, where ischemic stroke patients with higher CRP levels tend to suffer from a significantly worse outcome and mortality [9, 10].
S100β
S100β is a biomarker of ischemic stroke expressed by neuronal cells that can be released into the bloodstream when the BBB is compromised. Its concentration needs to be carefully balanced, as it may be protective in low concentrations, but at high levels has been shown to predict cerebral malignant infarction and correlate with infarct size [11, 12]. However, trial data on the use of biomarkers to guide clinical decisions leading to early decompressive surgery are currently lacking. Several studies have also uncovered an increase in S100β in ischemic stroke patients who present 1 to 7 days from symptom onset [13, 14]. In acute stroke patients, elevated S100β serum levels before thrombolytic therapy have also been demonstrated as a risk factor for HT [15].
N-terminal pro-brain natriuretic peptide
The brain natriuretic peptide (BNP) and its precursor, N-terminal proBNP (NT-proBNP), have been extensively studied as useful biomarkers for the prognosis and diagnosis of heart failure [16]. In recent years, BNP is gradually gaining recognition as a marker of atrial fibrillation (AF) and, therefore, as a biomarker to diagnose and predict stroke of cardioembolic origin [17, 18]. Plasma BNP levels have also been demonstrated to have significant correlations with infarct volume and National Institutes of Health stroke scale (NIHSS), making it a potentially powerful clinical biomarker for acute ischemic stroke [19].
Uric acid
Although uric acid has been adopted clinically for metabolic diseases, it is slowly garnering interest in the field of cardiovascular diseases due to its antioxidant properties. Despite data to suggest a strong association between uric acid levels and positive stroke outcomes [20, 21], several studies have observed an adverse relationship where higher uric acid levels were found to predict poor functional outcome and increased mortality [22, 23]. This disparity could highlight a dual role of uric acid in stroke, where both high and low levels of uric acid could adversely affect stroke outcomes [24]. Much remains to be explored for this biomarker before it could be roled out for use in stroke prognosis or diagnosis.
F2-isoprostanes
The product of arachidonic acid peroxidation generated by free radicals, F2-isoprostanes is well-established as a reliable biomarker for oxidative damage. Even though stroke is widely known as partly the result of oxidative damage, the relationship between F2-isoprostanes and human stroke remains poorly understood. Studies have demonstrated its importance in ischemic stroke as elevated levels of F2-isoprostanes could be observed in patients during the early course of stroke onset, with one even as early as three hours after [25–27].
Conclusion
Cerebral ischemia biomarkers have the potential to bridge translational gaps in medicine by shedding light on the pathological events leading to cerebral infarction and the ischemic cascade, aiding in clinical assessment during the critical time-sensitive decision-making process. Results in this area are still emerging, and more efforts could focus on ensuring the feasibility of incorporating stroke biomarkers for patient benefit. The translation of stroke biomarkers to clinical practice is challenging but can be extremely rewarding, especially when such concerted efforts of researchers, clinicians, industry partners and regulatory authorities result in a positive outcome for stroke patients.
Acknowledgements
We would like to thank the National Medical Research Council, Singapore (NMRC/CSA-SI/0003/2015, NMRC/CNIG/1115/2014 and NMRC/MOHIAFCat1/0015/2014) for their generous support.
References
1. GBD 2015 Mortality and Causes of Death Collaborators. Global, regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980-2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet 2016; 388(10053): 1459–1544.
2. NINDS rt-PA Stroke Study Group. Tissue plasminogen activator for acute ischemic stroke. N Engl J Med 1995; 333(24): 1581–1587.
3. Powers WJ, Derdeyn CP, Biller J, Coffey CS, Hoh BL, Jauch EC, et al. 2015 American Heart Association/American Stroke Association focused update of the 2013 guidelines for the early management of patients with acute ischemic stroke regarding endovascular treatment: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke 2015; 46(10): 3020–3035.
4. Seet RC, Rabinstein AA. Symptomatic intracranial hemorrhage following intravenous thrombolysis for acute ischemic stroke: a critical review of case definitions. Cerebrovasc Dis 2012; 34(2): 106–114.
5. Ng GJL, Quek AML, Cheung C, Arumugam TV, Seet RCS. Stroke biomarkers in clinical practice: a critical appraisal. Neurochem Int 2017; 107: 11–22.
6. Bustamante A, López-Cancio E, Pich S, Penalba A, Giralt D, García-Berrocoso T, et al. Blood biomarkers for the early diagnosis of stroke: The Stroke-Chip Study. Stroke 2017; 48(9): 2419–2425.
7. Whiteley W, Chong WL, Sengupta A, Sandercock P. Blood markers for the prognosis of ischemic stroke: a systematic review. Stroke 2009; 40(5): e380–389.
8. Barr TL, Latour LL, Lee KY, Schaewe TJ, Luby M, Chang GS, et al. Blood-brain barrier disruption in humans is independently associated with increased matrix metalloproteinase-9. Stroke 2010; 41(3): e123–128.
9. Muir KW, Weir CJ, Alwan W, Squire IB, Lees KR. C-reactive protein and outcome after ischemic stroke. Stroke 1999; 30(5): 981–985.
10. Idicula TT, Brogger J, Naess H, Waje-Andreassen U, Thomassen L. Admission C-reactive protein after acute ischemic stroke is associated with stroke severity and mortality: the ‘Bergen stroke study’. BMC Neurol 2009; 9: 18.
11. Vahedi K, Hofmeijer J, Juettler E, Vicaut E, George B, Algra A, et al. Early decompressive surgery in malignant infarction of the middle cerebral artery: a pooled analysis of three randomised controlled trials. Lancet Neurol 2007; 6(3): 215–222.
12. Abraha HD, Butterworth RJ, Bath PM, Wassif WS, Garthwaite J, Sherwood RA. Serum S-100 protein, relationship to clinical outcome in acute stroke. Ann Clin Biochem 1997; 34(Pt4): 366–370.
13. Aurell A, Rosengren LE, Karlsson B, Olsson JE, Zbornikova V, Haglid KG. Determination of S-100 and glial fibrillary acidic protein concentrations in cerebrospinal fluid after brain infarction. Stroke 1991; 22(10): 1254–1258.
14. Buttner T, Weyers S, Postert T, Sprengelmeyer R, Kuhn W. S-100 protein: serum marker of focal brain damage after ischemic territorial MCA infarction. Stroke 1997; 28(10): 1961–1965.
15. Foerch C, Wunderlich MT, Dvorak F, Humpich M, Kahles T, Goertler M, et al. Elevated serum S100B levels indicate a higher risk of hemorrhagic transformation after thrombolytic therapy in acute stroke. Stroke 2007; 38(9): 2491–2495.
16. Yancy CW, Jessup M, Bozkurt B, Butler J, Casey DE, Drazner MH, et al. 2013 ACCF/AHA Guideline for the management of heart failure: A report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines. Circulation 2013; 128(16): e240–327.
17. Naya T, Yukiiri K, Hosomi N, Takahashi T, Ohkita H, Mukai M, et al. Brain natriuretic peptide as a surrogate marker for cardioembolic stroke with paroxysmal atrial fibrillation. Cerebrovasc Dis 2008; 26(4): 434–440.
18. Fonseca AC, Matias JS, Pinho e Melo T, Falcao F, Canhao P, Ferro JM. N-terminal probrain natriuretic peptide as a biomarker of cardioembolic stroke. Int J Stroke 2011; 6(5): 398–403.
19. Tomita H, Metoki N, Saitoh G, Ashitate T, Echizen T, Katoh C, et al. Elevated plasma brain natriuretic peptide levels independent of heart disease in acute ischemic stroke: correlation with stroke severity. Hypertens Res 2008; 31(9): 1695–1702.
20. Amaro S, Urra X, Gomez-Choco M, Obach V, Cervera A, Vargas M, et al. Uric acid levels are relevant in patients with stroke treated with thrombolysis. Stroke 2011; 42(1 Suppl): S28–32.
21. Chamorro A, Obach V, Cervera A, Revilla M, Deulofeu R, Aponte JH. Prognostic significance of uric acid serum concentration in patients with acute ischemic stroke. Stroke 2002; 33(4): 1048–1052.
22. Weir CJ, Muir SW, Walters MR, Lees KR. Serum urate as an independent predictor of poor outcome and future vascular events after acute stroke. Stroke 2003; 34(8): 1951–1956.
23. Karagiannis A, Mikhailidis DP, Tziomalos K, Sileli M, Savvatianos S, Kakafika A, et al. Serum uric acid as an independent predictor of early death after acute stroke. Circ J 2007; 71(7): 1120–1127.
24. Seet RC, Kasiman K, Gruber J, Tang SY, Wong MC, Chang HM, et al. Is uric acid protective or deleterious in acute ischemic stroke? A prospective cohort study. Atherosclerosis 2010; 209(1): 215–219.
25. Sanchez-Moreno C, Dashe JF, Scott T, Thaler D, Folstein MF, Martin A. Decreased levels of plasma vitamin C and increased concentrations of inflammatory and oxidative stress markers after stroke. Stroke 2004; 35(1): 163–168.
26. Ward NC, Croft KD, Blacker D, Hankey GJ, Barden A, Mori TA, et al. Cytochrome P450 metabolites of arachidonic acid are elevated in stroke patients compared with healthy controls. Clin Sci (Lond) 2011; 121(11): 501–507.
27. Seet RC, Lee CY, Chan BP, Sharma VK, Teoh HL, Venketasubramanian N, et al. Oxidative damage in ischemic stroke revealed using multiple biomarkers. Stroke 2011; 42(8): 2326–2329.
The authors
Geelyn J.L. Ng1,2 BSc, Raymond C.S. Seet*1,2 MBBS, MRCP (UK), MMed (Int Med), FRCP (UK)
1Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
2Division of Neurology, Department of Medicine, National
University Health System, Singapore
*Corresponding author
E-mail: raymond_seet@nuhs.edu.sg
Clostridium difficile diagnosis: not always a bed of roses
, /in Featured Articles /by 3wmediaClostridium difficile is a leading cause of nosocomial diarrhoea and one of the most common healthcare-associated infections. A dramatic worldwide increase in the incidence of C. difficile infection has occurred over the past two decades with the emergence of hypervirulent strains. Accurate and timely laboratory diagnosis of C. difficile infection is fundamental to ensure patients receive appropriate treatment and proper counter-infection measures are put in place. However, the availability of many commercial tests with different C. difficile targets contributes to uncertainty and controversy around the optimal diagnostic algorithm.
by Dr Guilherme Grossi Lopes Cançado, Prof. Rodrigo Otávio Silveira Silva and Prof. Eduardo Garcia Vilela
Introduction
Clostridium difficile is a major cause of healthcare-associated diarrhoea, and is linked to significant morbidity, economic burden and even mortality. Disagreement between diagnostic tests is an ongoing barrier to clinical decision-making and epidemiological surveillance. With the increasing number and severity of Clostridium difficile infections (CDI) after the emergence of the epidemic BI/NAP1/027 strain in the 2000s, there has been a renewed interest in optimizing the laboratory diagnosis of this infection.
Testing for C. difficile
Cytotoxin neutralization, toxigenic culture and toxin enzyme immunoassay
The two most accurate methods for CDI diagnosis are cytotoxin neutralization (CTN) and toxigenic culture (TC). CTN has long been used as a reference method for C. difficile detection, although different protocols have been proposed. Basically, this technique consists of inoculating a filtrate of a stool suspension into a cell culture (Vero, Hep2, fibroblasts, CHO or HeLa cells) and observing a cytopathic effect (such as cell rounding) as a consequence of disruption of the cell cytoskeleton 24–48 h later. CDI confirmation is obtained by the addition of a specific antiserum directed against C. difficile or against C. sordellii, neutralizing the toxin effects. Studies performed in the last 10 years, however, demonstrated that the sensitivities of CTN protocols range between 60 and 86%, when compared with toxigenic culture. Although culture was found to be the most sensitive method for detecting C. difficile in feces, it is not very specific owing to the possibility of isolating non-toxigenic strains. In order to overcome this issue, it should always be combined with a toxin detection method, such as enzyme immunoassay (EIA), direct cytopathic effect on cell lines or the identification of toxin-related genes by PCR. This notwithstanding, both techniques are time consuming, laborious and require trained personnel, reasons why they are not frequently used in daily practice [1].
In this context, commercial rapid EIA and DNA-based tests are currently the most widely used tools for CDI diagnosis. EIA for toxin detection is fast, cheap, easy to perform and does not require technical training or special equipment: characteristics which have favored its use in low income countries. However, several studies have reported low detection sensitivities of different commercial kits (approximately 50–70%), making toxin EIAs inadequate as standalone tests [2]. Some authors have suggested the analysis of sequential samples from the same patient, but this practice did not significantly increase the positive predictive value of the test and may even amplify the rate of false positives. Furthermore, toxin tests can be falsely negative, which can be due to previous antibiotic treatment, pre-analytic toxin degradation or sampling error (e.g., ileus, fecal dilution). Consequently, toxin EIA may be sufficient and cost-effective as a screening test in clinical settings where there is a low prevalence of CDI, but not for epidemic scenarios.
Detection of glutamate dehydrogenase
Another method that has been used to diagnose CDI is the detection of glutamate dehydrogenase (GDH), a metabolic enzyme constitutionally produced almost exclusively by C. difficile, which is significantly more sensitive than toxin A and B EIAs. We have recently shown that GDH rapid immunoassay presents 100% sensitivity and negative predictive value, compared with the culture-based method, in accordance with order authors [3]. Cheng et al. have advocated the use of GDH in order to improve the diagnostic capacity and control of potential outbreaks of CDI in developing countries, as this test is five to ten times cheaper than molecular assays [4]. In fact, we have recently reported a significant increase in CDI treatment rates in a university hospital of Brazil (from 53.8% to 100%) simply after replacing the toxin EIA by the rapid GDH immunoassay as a screening test [3]. This finding supports the use of GDH in countries with limited economic resources, as it is simple to perform and, unlike PCR, requires no special facilities or personnel qualifications that might restrict its use. Although sensitive, GDH lacks specificity, because it only indicates the presence of the microorganism, instead of toxin production. In this context, a concern with the overdiagnosis and overtreatment of patients with diarrhoea and C. difficile colonization may arise. A negative test can almost rule out CDI and avoid the need for more expensive toxin testing, but a positive GDH assay should preferably be followed by toxin-based diagnostic methods before one can come to a safe conclusion on infection. Asymptomatic carriage of C. difficile occurs in 5–15% of healthy adults, but may be as high as 90% in newborns and healthy infants, and up to 51% in residents in long-term care facilities [5]. In this way, the incorporation of a two-step strategy, including a sensitive organism-based test for screening, such as GDH, followed by a toxin test for confirmation of clinically significant disease, is a reasonable approach. Combined tests including GDH and toxin detection in one easy-to-use cartridge have been recently developed, but several authors have demonstrated limited sensitivity of the toxin component. In our study, the toxin component presented an even lower sensitivity than conventional toxin EIA (50% vs 58%), compared with toxigenic culture [3]. In this way, GDH+/toxin− samples would still have to be submitted to a third test (in a multistep algorithm) to rule out infection, increasing time to diagnosis and health costs. However, some studies have shown that, even without treatment, patients with toxin-negative stool specimens have shorter diarrhoea duration than those with toxin-positive stool specimens. These findings may suggest a limited need for CDI treatment for GDH-positive patients and toxin-negative stool specimens [6].
Molecular testing and rapid diagnosis
In 2009, facing an epidemic of CDI due to hypervirulent C. difficile strains, the US FDA cleared the first commercial molecular test for rapid CDI diagnosis [7]. Shortly afterwards, hospitals in North America and Europe began switching to DNA-based testing strategies as a method of choice for the diagnosis of C. difficile. Nucleic acid amplification testing (NAAT), including rapid testing PCR and loop-mediated isothermal amplification (LAMP), can detect the tcdA/tcdB genes (regulate toxin A/B production) or the tcdC gene (a negative regulator of toxin A and B production) and identify the presence of toxigenic C. difficile in a single step. It has a higher sensitivity (90–95%) and specificity (95–96%) than toxin EIAs and has a rapid turnaround time, but requires specialized equipment and personnel. It is worth noting that the Gene-Xpert® system can also simultaneously indicate the presence of the potentially ‘hypervirulent’ ribotype 027 strain, giving important epidemiological information. Nonetheless, although a PCR assay can identify toxin genes, it cannot detect the presence of toxin. Several studies have shown that toxin−/C. difficile+ patients present shorter duration of symptoms and better outcomes than toxin+/C. difficile+ individuals, demonstrating that this subpopulation may have either mild CDI or colonization, and even not need to be treated. In this way, some authors have questioned the use molecular tests as standalone tests because of the high likelihood of overdiagnosis and overtreatment [8]. However, there may be a role for identifying carriers to prevent transmission and this issue should be better addressed in future studies.
C. difficile testing protocol
Using reliable and rapid diagnostic tests, such as NAAT, practitioners could offer appropriate treatment earlier, thereby sparing patients a time-consuming evaluation and unnecessary antibiotic therapy and its complications. Despite worldwide advances in analytical technology, transport systems and computerization, many laboratories in developing countries have difficulties in improving turnaround times and diagnostic capability. The optimal diagnostic algorithm for CDI is yet to be adequately defined and may vary according to the underlying clinical and laboratory circumstances. We believe that the decision about which test(s) to use is determined by a combination of what is practical and feasible in a specific setting. In Brazil, for example, where only toxin EIA was available for CDI diagnosis until 2015, the introduction of the GDH test resulted in a dramatic increase in C. difficile treatment rates [3]. All of the reference methods, CTN, toxigenic culture, or PCR, require advanced infrastructure and expensive testing. Smaller, community-based hospitals, where much of C. difficile testing is currently performed, may not have the financial means to establish these methods nor have the staff to perform the time-consuming, highly complex assays. In this way, using GDH–toxin A/B assays may be an adequate option for diagnostic algorithms in developing countries, whereas molecular techniques, toxigenic culture or CTN may be reserved for discordant samples (Figure 1). Future studies should focus on developing simple diagnostic approaches to accurately distinguish active infection from mere colonization.
References
1. Delmée M. Laboratory diagnosis of Clostridium difficile disease. Clin Microbiol Infect 2001; 7(8): 411–416.
2. Silva RO, Vilela EG, Neves MS, Lobato FC. Evaluation of three enzyme immunoassays and a nucleic acid amplification test for the diagnosis of Clostridium difficile-associated diarrhea at a university hospital in Brazil. Rev Soc Bras Med Trop 2014; 47(4): 447–450.
3. Cançado GGL, Silva ROS, Nader AP, Lobato FCF, Vilela EG. Impact of simultaneous glutamate dehydrogenase (GDH) and toxin A/B rapid immunoassay on Clostridium difficile diagnosis and treatment in hospitalized patients with antibiotic-associated diarrhea in a university hospital of Brazil. J Gastroenterol Hepatol 2017; doi: 10.1111/jgh.13901 [Epub ahead of print].
4. Cheng JW, Xiao M, Kudinha T, Xu ZP, Sun LY, Hou X, Zhang L, Fan X, Kong F, Xu YC. The role of glutamate gehydrogenase (GDH) testing assay in the diagnosis of Clostridium difficile infections: a high sensitive screening test and an essential step in the proposed laboratory diagnosis workflow for developing countries like China. PLoS One 2015; 10(12): e0144604.
5. Furuya-Kanamori L, Marquess J, Yakob L, Riley TV, Paterson DL, Foster NF, Huber CA, Clements AC. Asymptomatic Clostridium difficile colonization: epidemiology and clinical implications. BMC Infect Dis 2015; 15: 516.
6. Yuhashi K, Yagihara Y, Misawa Y, Sato T, Saito R, Okugawa S, Moriya K. Diagnosing Clostridium difficile-associated diarrhea using enzyme immunoassay: the clinical significance of toxin negativity in glutamate dehydrogenase-positive patients. Infect Drug Resist 2016; 9: 93–99.
7. Polage CR, Turkiewicz JV, Cohen SH. The never-ending struggle with laboratory testing for Clostridium difficile infection. J Comp Eff Res 2016; 5(2): 113–116.
8. Polage CR, Gyorke CE, Kennedy MA, Leslie JL, Chin DL, Wang S, Nguyen HH, Huang B, Tang YW, Lee LW, Kim K, Taylor S, Romano PS, Panacek EA, Goodell PB, Solnick JV, Cohen SH. Overdiagnosis of Clostridium difficile infection in the molecular test era. JAMA Intern Med 2015; 175(11): 1792–1801.
The authors
Guilherme Grossi Lopes Cançado*1,2 MD, Rodrigo Otávio Silveira Silva3 PhD, and Eduardo Garcia Vilela1 MD, PhD
1Instituto Alfa de Gastroenterologia,
Federal University of Minas Gerais, Brazil.
2Department of Gastroenterology,
Hospital da Polícia Militar de Minas Gerais, Brazil.
3Veterinary School, Federal University of Minas Gerais, Brazil.
*Corresponding author
E-mail: guilhermegrossi@terra.com.br
Literarure Review: Brain Biomarkers
, /in Featured Articles /by 3wmediaPrognostic value of molecular and imaging biomarkers in patients with supratentorial glioma
Lopci E, Riva M, Olivari L, Raneri F, Soffietti R, et al. Eur J Nucl Med Mol Imaging 2017; 44(7): 1155–1164
PURPOSE: We evaluated the relationship between 11C-methionine PET (11C-METH PET) findings and molecular biomarkers in patients with supratentorial glioma who underwent surgery.
METHODS: A consecutive series of 109 patients with pathologically proven glioma (64 men, 45 women; median age 43 years) referred to our Institution from March 2012 to January 2015 for tumour resection and who underwent preoperative 11C-METH PET were analysed. Semi-quantitative evaluation of the 11C-METH PET images included SUVmax, region of interest-to-normal brain SUV ratio (SUVratio) and metabolic tumour volume (MTV). Imaging findings were correlated with disease outcome in terms of progression-free survival (PFS), and compared with other clinical biological data, including IDH1 mutation status, 1p/19q codeletion and MGMT promoter methylation. The patients were monitored for a mean period of 16.7 months (median 13 months).
RESULTS: In all patients, the tumour was identified on 11C-METH PET. Significant differences in SUVmax, SUVratio and MTV were observed in relation to tumour grade (P<0.001). IDH1 mutation was found in 49 patients, 1p/19q codeletion in 58 patients and MGMT promoter methylation in 74 patients. SUVmax and SUVratio were significantly inversely correlated with the presence of IDH1 mutation (P<0.001). Using the 2016 WHO classification, SUVmax and SUVratio were significantly higher in patients with primary glioblastoma (IDH1-negative) than in those with other diffuse gliomas (P<0.001). Relapse or progression was documented in 48 patients (median PFS 8.7 months). Cox regression analysis showed that SUVmax and SUVratio, tumour grade, tumour type on 2016 WHO classification, IDH1 mutation status, 1p/19q codeletion and MGMT promoter methylation were significantly associated with PFS. None of these factors was found to be an independent prognostic factor in multivariate analysis.
CONCLUSION: 11C-METH PET parameters are significantly correlated with histological grade and IDH1 mutation status in patients with glioma. Grade, pathological classification, molecular biomarkers, SUVmax and SUVratio were prognostic factors for PFS in this cohort of patients. The trial was registered with ClinicalTrials.gov (registration: NCT02518061).
Expression of cell cycle regulators and biomarkers of proliferation and regrowth in human pituitary adenomas
Gruppetta M Formosa R, Falzon S, Ariff Scicluna S, Falzon E, et al. Pituitary 2017; 20(3): 358–371
PURPOSE: The pathogenesis of pituitary adenomas (PA) is complex. Ki-67, pituitary tumour transforming gene (PTTG), vascular endothelial growth factor (VEGF), cyclin D1, c-MYC and pituitary adenylate cyclase-activating peptide (PACAP) protein expression was analysed and correlated with tumour and patient characteristics.
METHODS: 74 pituitary tumour samples (48 non-functional PA, 26 functional PAs); immunohistochemical analysis of protein expression, retrospective analysis of MR images and in vitro analysis of octreotide treatment was carried out on GH3 cells.
RESULTS: PTTG expression was negatively associated with age and positively with PA size, regrowth and Ki-67 index. Cyclin D1 correlated with Ki-67 and tumour size. c-MYC negatively correlated with size of tumour and age, and correlated with PTTG expression. Somatostatin analogue treatment was associated with lower Ki-67, PTTG and cyclin D1 expression while T2 hypointense PAs were associated with lower PTTG, cyclin D1, c-MYC and Ki-67. In vitro analyses confirmed the effect of somatostatin analogue treatment on PTTG and cyclin D1 expression.
CONCLUSIONS: Interesting and novel observations on the differences in expression of tumour markers studied are reported. Correlation between Ki-67 expression, PTTG nuclear expression and recurrence/regrowth of PAs, emphasizes the role that Ki-67 and PTTG expression have as markers of increased proliferation. c-MYC and PTTG nuclear expression levels were correlated providing evidence that PTTG induces c-MYC expression in PAs and we propose that c-MYC might principally have a role in early pituitary tumorigenesis. Evidence is shown that the anti-proliferative effect of somatostatin analogue treatment in vivo occurs through regulation of the cell cycle.
Comparison of multiple tau PET measures as biomarkers in aging and Alzheimer’s Disease
Maass A, Landau S, Baker SL, Horng A, Lockhart SN, et al. Neuroimage 2017; 157: 448–463
The recent development of tau-specific positron emission tomography (PET) tracers enables in vivo quantification of regional tau pathology, one of the key lesions in Alzheimer’s disease (AD). Tau PET imaging may become a useful biomarker for clinical diagnosis and tracking of disease progression but there is no consensus yet on how tau PET signal is best quantified. The goal of the current study was to evaluate multiple whole-brain and region-specific approaches to detect clinically relevant tau PET signal. Two independent cohorts of cognitively normal adults and amyloid-positive (Aβ+) patients with mild cognitive impairment (MCI) or AD-dementia underwent [18F]AV-1451 PET. Methods for tau tracer quantification included: (i) in vivo Braak staging, (ii) regional uptake in Braak composite regions, (iii) several whole-brain measures of tracer uptake, (iv) regional uptake in AD-vulnerable voxels, and (v) uptake in a priori defined regions. Receiver operating curves characterized accuracy in distinguishing Aβ− controls from AD/MCI patients and yielded tau positivity cut-offs. Clinical relevance of tau PET measures was assessed by regressions against cognition and MR imaging measures. Key tracer uptake patterns were identified by a factor analysis and voxel-wise contrasts. Braak staging, global and region-specific tau measures yielded similar diagnostic accuracies, which differed between cohorts. While all tau measures were related to amyloid and global cognition, memory and hippocampal/entorhinal volume/thickness were associated with regional tracer retention in the medial temporal lobe. Key regions of tau accumulation included medial temporal and inferior/middle temporal regions, retrosplenial cortex, and banks of the superior temporal sulcus. Our data indicate that whole-brain tau PET measures might be adequate biomarkers to detect AD-related tau pathology. However, regional measures covering AD-vulnerable regions may increase sensitivity to early tau PET signal, atrophy and memory decline.
C-terminal fragments of the amyloid precursor protein in cerebrospinal fluid as potential biomarkers for Alzheimer disease
García-Ayllón MS, Lopez-Font I, Boix CP, Fortea J, Sánchez-Valle R, et al. Sci Rep. 2017; 7(1): 2477
This study assesses whether C-terminal fragments (CTF) of the amyloid precursor protein (APP) are present in cerebrospinal fluid (CSF) and their potential as biomarkers for Alzheimer’s disease (AD). Immunoprecipitation and simultaneous assay by Western blotting using multiplex fluorescence imaging with specific antibodies against particular domains served to characterize CTFs of APP in human CSF. We demonstrate that APP-CTFs are detectable in human CSF, being the most abundant a 25-kDa fragment, probably resulting from proteolytic processing by η-secretase. The level of the 25-kDa APP-CTF was evaluated in three independent CSF sample sets of patients and controls. The CSF level of this 25-kDa CTF is higher in subjects with autosomal dominant AD linked to PSEN1 mutations, in demented Down syndrome individuals and in sporadic AD subjects compared to age-matched controls. Our data suggest that APP-CTF could be a potential diagnostic biomarker for AD.
Blood-based biomarkers for the identification of sports-related concussion
Anto-Ocrah M, Jones CMC, Diacovo D, Bazarian JJ. Neurol Clin 2017; 35(3): 473–485
Sports-related concussions (SRCs) are common among athletes in the United States. Most athletes who sustain an SRC recover within 7 to 10 days; however, many athletes who sustain the injury do not recover as expected and experience prolonged, persistent symptoms. In this document, the authors provide an overview of the empirical evidence related to the use of blood-based brain biomarkers in the athlete population for diagnosis of SRCs, prognosis of recovery and return to play guidelines, and indications of neurodegeneration. The authors also provide a summary of research challenges, gaps in the literature, and future directions for research.
Brain biomarkers and pre-injury cognition are associated with long-term cognitive outcome in children with traumatic brain injury
Wilkinson AA, Dennis M, Simic N, Taylor MJ, Morgan BR, et al. BMC Pediatr 2017; 17(1): 173
BACKGROUND: Children with traumatic brain injury (TBI) are frequently at risk of long-term impairments of attention and executive functioning but these problems are difficult to predict. Although deficits have been reported to vary with injury severity, age at injury and sex, prognostication of outcome remains imperfect at a patient-specific level. The objective of this proof of principle study was to evaluate a variety of patient variables, along with six brain-specific and inflammatory serum protein biomarkers, as predictors of long-term cognitive outcome following pediatric TBI.
METHOD: Outcome was assessed in 23 patients via parent-rated questionnaires related to attention deficit hyperactivity disorder (ADHD) and executive functioning, using the Conners 3rd Edition Rating Scales (Conners-3) and Behaviour Rating Inventory of Executive Function (BRIEF) at a mean time since injury of 3.1 years. Partial least squares (PLS) analyses were performed to identify factors measured at the time of injury that were most closely associated with outcome on (1) the Conners-3 and (2) the Behavioural Regulation Index (BRI) and (3) Metacognition Index (MI) of the BRIEF.
RESULTS: Higher levels of neuron specific enolase (NSE) and lower levels of soluble neuron cell adhesion molecule (sNCAM) were associated with higher scores on the inattention, hyperactivity/impulsivity and executive functioning scales of the Conners-3, as well as working memory and initiate scales of the MI from the BRIEF. Higher levels of NSE only were associated with higher scores on the inhibit scale of the BRI.
CONCLUSIONS: NSE and sNCAM show promise as reliable, early predictors of long-term attention-related and executive functioning problems following pediatric TBI.
Biomarkers of stroke recovery: Consensus-based core recommendations from the Stroke Recovery and Rehabilitation Roundtable
Boyd LA, Hayward KS, Ward NS, Stinear CM, Rosso C, et al. Int J Stroke 2017; 12(5): 480-493
The most difficult clinical questions in stroke rehabilitation are “What is this patient’s potential for recovery?” and “What is the best rehabilitation strategy for this person, given her/his clinical profile?” Without answers to these questions, clinicians struggle to make decisions regarding the content and focus of therapy, and researchers design studies that inadvertently mix participants who have a high likelihood of responding with those who do not. Developing and implementing biomarkers that distinguish patient subgroups will help address these issues and unravel the factors important to the recovery process. The goal of the present paper is to provide a consensus statement regarding the current state of the evidence for stroke recovery biomarkers. Biomarkers of motor, somatosensory, cognitive and language domains across the recovery timeline post-stroke are considered; with focus on brain structure and function, and exclusion of blood markers and genetics. We provide evidence for biomarkers that are considered ready to be included in clinical trials, as well as others that are promising but not ready and so represent a developmental priority. We conclude with an example that illustrates the utility of biomarkers in recovery and rehabilitation research, demonstrating how the inclusion of a biomarker may enhance future clinical trials. In this way, we propose a way forward for when and where we can include biomarkers to advance the efficacy of the practice of, and research into, rehabilitation and recovery after stroke.
Brain biomarkers of vulnerability and progression to psychosis
Cannon TD. Schizophr Bull 2016; 42(Suppl 1): S127–132
Identifying predictors and elucidating the fundamental mechanisms underlying onset of psychosis are critical for the development of targeted pre-emptive interventions. This article presents a selective review of findings on risk prediction algorithms and potential mechanisms of onset in youth at clinical high-risk for psychosis, focusing principally on recent findings of the North American Prodrome Longitudinal Study (NAPLS). Multivariate models incorporating risk factors from clinical, demographic, neurocognitive, and psychosocial assessments achieve high levels of predictive accuracy when applied to individuals who meet criteria for a prodromal risk syndrome. An individualized risk calculator is available to scale the risk for newly ascertained cases, which could aid in clinical decision making. At risk individuals who convert to psychosis show elevated levels of proinflammatory cytokines, as well as disrupted resting state thalamo-cortical functional connectivity at baseline, compared with those who do not. Further, converters show a steeper rate of grey matter reduction, most prominent in prefrontal cortex, that in turn is predicted by higher levels of inflammatory markers at baseline. Microglia, resident immune cells in the brain, have recently been discovered to influence synaptic plasticity in health and impair plasticity in disease. Processes that modulate microglial activation may represent convergent mechanisms that influence brain dysconnectivity and risk for onset of psychosis and thus may be targetable in developing and testing preventive interventions.
Literature Review: Gastrointestinal infections
, /in Featured Articles /by 3wmediaMultiplex RT-PCR for rapid detection of viruses commonly causing diarrhoea in pediatric patients
Thongprachum A, Khamrin P, Pham NT, Takanashi S, Okitsu S, et al. J Med Virol 2017; 89(5): 818–824
Multiplex RT-PCR method using five sets of panel primers was developed for the detection of diarrhoeal viruses, including rotavirus A, B, and C, adenovirus, astrovirus, norovirus GI and GII, sapovirus, Aichi virus, parechovirus, enterovirus, cosavirus, bocavirus, and Saffold virus. The sensitivity of the method was evaluated and tested with 751 fecal specimens collected from Japanese children with acute diarrhoea. Several kinds of viruses were detected in 528 out of 751 (70.3%) fecal specimens. Mixed-infection with different viruses in clinical specimens could also be effectively detected. The method proved to be reliable with highly sensitive and specific and useful for routine diagnosis.
Evaluation of diagnostic accuracy of two rapid stool antigen tests using an immunochromatographic assay to detect Helicobacter pylori
da Silva-Etto JMK1, Mattar R2, Villares-Lopes CA1, Marques SB1, Carrilho FJ. Clin Biochem 2017; pii: S0009–9120(17)30129–7
OBJECTIVES: The stool antigen assay for H. pylori infection diagnosis with monoclonal antibodies is a simple and recommended technique by the Maastricht V/Florence consensus report. Recently, Pylori K-Set K-1219 (Coris Bioconcept Sprl, Belgium) and HP-F23 (Symbiosys, Brazil) have been made commercially available in Brazil. Thus, the aim of this study was to evaluate the diagnostic accuracies of these two rapid stool antigen tests by immunochromatographic assays (index tests) for the clinical practice.
DESIGN AND METHODS: A total of 98 patients who underwent upper gastrointestinal endoscopy and 13C-urea breath test entered the study. H. pylori infection status was defined by the combination of the rapid urease test and the 13C-urea breath test (reference standard). Two observers who were aware of H. pylori status performed the reading of index tests. Diagnostic accuracy (sensitivity, specificity, positive predictive value, negative predictive value with 95% confidence intervals, positive likelihood ratio, negative likelihood ratio and kappa index measure of agreement) were determined.
RESULTS: The index tests where in perfect agreement with the H. pylori status with kappa values of 0.87 for Pylori K-Set K-1219 and 0.92 for HP-F23. The sensitivity of HP-F23 was 97.9% (IC95%: 87.5–100) and specificity was 93.8% (IC95%; 84-97.2).The positive likelihood ratio was 15.8, and the negative likelihood ratio was 0.02. The Pylori K-Set K-1219 had a sensitivity of 87.7% (IC95%: 74.5–94.9) and a specificity of 100% (IC95%: 91.6-100); the positive likelihood ratio was infinity, and the negative likelihood ratio was 0.1. The test line on the cassette device of HP-F23 was stronger than of the Pylori K-Set K-1219.
CONCLUSION: The HP-F23 test performed better in clinical practice. Nonetheless, the 13C-urea breath test is more reliable technique. Moreover, caution must be paid to the trace or clear pale test line readings that were observed in false positive and false negative results, leading to incorrect management of the patient.
Development of an LPS-based ELISA for diagnosis of Yersinia enterocolitica O:3 infections in Danish patients: a follow-up study
Dalby T, Rasmussen E, Schiellerup P, Krogfelt KA. BMC Microbiol 2017; 17(1): 125
BACKGROUND: The bacterium Yersinia enterocolitica causes gastroenteritis in humans. The study aimed to develop a diagnostic enzyme-linked immunosorbent assay (ELISA) for detection of Y. enterocolitica O:3 LPS antibodies in sera from Danish patients with suspected Y. enterocolitica O:3 gastrointestinal infection. As a part of this, antibody decay profiles after culture confirmed Y. enteritis were studied.
RESULTS: An ELISA using Y. enterocolitica O:3 LPS as the coating antigen was developed for measuring IgA, IgG and IgM specific antibodies. A longitudinal collection of 220 sera drawn between 20 and 1053 days after onset of symptoms from 85 adult Danish patients with verified Y. enteritis were examined. A control group of 100 sera from healthy Danish blood-donors were analysed in order to determine the cut-off for interpretation of results. Serum samples from 62 out of 81 patients who delivered either the first or the second sample were found positive for specific antibodies against Y. enterocolitica O:3 LPS (77%). For samples collected within 60 days after onset of symptoms (n = 48) sensitivities of 58%, 42% and 79% for IgA, IgG and IgM antibodies were found. A sensitivity of 81% was found for these samples when using the definition of a positive result in either IgA, IgG or IgM as a combined positive. All samples received up to 36 days after onset of symptoms (n=10) were found to be positive using this definition. For the period 61 to 90 days after onset of symptoms (n=32), a combined sensitivity of 63% was found. The antibody levels as well as decay profiles for the three different immunoglobulin classes for the individual patients exhibited a large degree of variation.
CONCLUSIONS: Using a definition of positive as a positive result for either IgA, IgG or IgM antibodies, a diagnostic sensitivity of 81% was achieved for samples received within 60 days after onset of symptoms. In particular, the levels of specific IgM antibodies were elevated. In comparison, the standard tube-agglutination assay achieved a sensitivity of 60% on the same samples. The sensitivity of the ELISA decreased the longer the duration of time since onset of symptoms. The ELISA was highly specific for Yersinia when testing sera from individuals with confirmed gastrointestinal infections by other bacteria. Moreover, the knowledge gained from this longitudinal study of antibody decay profiles can be used in future epidemiological studies of seroprevalence.
The development of a multiplex real-time RT-PCR for the detection of adenovirus, astrovirus, rotavirus and sapovirus from stool samples
Bennett S, Gunson RN. J Virol Methods 2017; 242: 30–34
Viral gastroenteritis is a major health problem with significant morbidity and economic consequences. Viral gastroenteritis is caused by a number of viruses, including norovirus, rotavirus, adenovirus, astrovirus, and sapovirus. Conventional diagnosis is based on direct antigen detection and electron microscopy, however enzyme immunoassay’s are insensitive and not available for all relevant pathogens, and electron microscope (EM) is no longer routinely carried out in most laboratories. Most laboratories now offer norovirus real-time PCR testing however the availability of other assays is variable. Commercial methods for the detection of inflectional intestinal disease (IID) are available but these can be expensive and are not commonly used. This paper describes the development of a single multiplex assay for the simultaneous detection of adenovirus, astrovirus, rotavirus and sapovirus from stool samples. The multiplex was evaluated by assessing endpoint sensitivity, specificity, panel of clinical samples, quality control (QC) panel and the robustness and reproducibility of the multiplex.
Cholera rapid test with enrichment step has diagnostic performance equivalent to culture
Ontweka LN, Deng LO, Rauzier J, Debes AK, Tadesse F, et al. PLoS One 2016; 11(12): e0168257
Cholera rapid diagnostic tests (RDT) could play a central role in outbreak detection and surveillance in low-resource settings, but their modest performance has hindered their broad adoption. The addition of an enrichment step may improve test specificity. We describe the results of a prospective diagnostic evaluation of the Crystal VC RDT (Span Diagnostics, India) with enrichment step and of culture, each compared to polymerase chain reaction (PCR), during a cholera outbreak in South Sudan. RDTs were performed on alkaline peptone water inoculated with stool and incubated for 4-6 hours at ambient temperature. Cholera culture was performed from wet filter paper inoculated with stool. Molecular detection of Vibrio cholerae O1 by PCR was done from dry Whatman 903 filter papers inoculated with stool, and from wet filter paper supernatant. In August and September 2015, 101 consecutive suspected cholera cases were enrolled, of which 36 were confirmed by PCR. The enriched RDT had 86.1% (95% CI: 70.5–95.3) sensitivity and 100% (95% CI: 94.4–100) specificity compared to PCR as the reference standard. The sensitivity of culture versus PCR was 83.3% (95% CI: 67.2–93.6) for culture performed on site and 72.2% (95% CI: 54.8–85.8) at the international reference laboratory, where samples were tested after an average delay of two months after sample collection, and specificity was 98.5% (95% CI: 91.7–100) and 100% (95% CI: 94.5–100), respectively. The RDT with enrichment showed performance comparable to that of culture and could be a sustainable alternative to culture confirmation where laboratory capacity is limited.
Clinical and analytical evaluation of a single-vial stool collection device with formalin-free fixative for improved processing and comprehensive detection of gastrointestinal parasites
Couturier BA, Jensen R, Arias N, Heffron M, Gubler E, et al. J Clin Microbiol 2015; 53(8): 2539–2548
Microscopic examination of feces is a standard laboratory method for diagnosing gastrointestinal parasite infections. In North America, the ovum and parasite (O&P) examination is typically performed using stool that is chemically fixed in polyvinyl alcohol (PVA) and formalin, after which the stool is concentrated by filtration to enhance sensitivity. Mini Parasep solvent-free (SF) tubes allow collection and concentration within a single collection vial. The goal of the study was to determine whether consolidated processing and concentration with the Parasep tubes using an alcohol-based fixative (Alcorfix) provide O&P examinations equivalent to or better than those done by processing of PVA-formalin-fixed stool using a SpinCon concentration device. Parasep tubes revealed filtration performance equivalent to that of the SpinCon concentration device using PVA-formalin-fixed stool containing protozoa. Specimens cocollected in Parasep tubes containing PVA-formalin and Alcorfix revealed comparable morphology and staining for various protozoa. Alcorfix effectively fixed live Cryptosporidium and microsporidia such that morphology and staining were conserved for modified acid-fast and modified trichrome stains. A work flow analysis revealed significant time savings for batches of 10 or 30 O&P specimens in tubes with Alcorfix compared to the amount of time that it took to analyse the same number of specimens in tubes with PVA-formalin. The direct hands-on time savings with Mini Parasep tubes were 17 min and 41 s and 32 min and 1 s for batches of 10 and 30 specimens, respectively. Parasep tubes containing Alcorfix provide significant work flow advantages to laboratories that process medium to high volumes of O&P specimens by streamlining processing and converting to a single tube. These improvements in work flow, reduction of the amount of formalin used in the laboratory, and equivalent microscopy results are attractive advancements in O&P testing for North American diagnostic parasitology laboratories.
Chemiluminescent immunoassays for the laboratory diagnosis of Clostridium difficile infection
Makristathis A, Zeller I, Mitteregger D, Kundi M, Hirschl AM. Eur J Clin Microbiol Infect Dis 2017; 36(7): 1253–1259
For the microbiological diagnosis of a Clostridium difficile infection (CDI), a two-test algorithm consisting of a C. difficile glutamate dehydrogenase (GDH)-immunoassay followed by a toxin-immunoassay in positive cases is widely used. In this study, two chemiluminescent immunoassays (CLIAs), one for GDH and the other for the toxins A and B, have been evaluated systematically using appropriate reference methods. Three-hundred diarrhoeal stool specimens submitted for CDI diagnosis were analysed by the LIAISON CLIAs (DiaSorin). Toxigenic culture (TC) and cell cytotoxicity assay (CCTA) were used as “gold standard” reference methods. In addition, GDH and toxin A and B enzyme immunoassays (EIAs), C. diff Chek-60 and toxin A/B II (TechLab), and the Cepheid Xpert C. difficile polymerase chain reaction (PCR) were performed. C. difficile was grown in 42 (14%), TC was positive in 35 (11.7%) and CCTA in 25 (8.3%) cases. CLIAs were more sensitive but less specific than the respective EIAs. Using culture as reference, the sensitivity of the GDH CLIA was 100%. In comparison to CCTA sensitivity, specificity, positive predictive value and negative predictive value of the two-test algorithm were 88, 99.3, 91.7 and 98.9% by CLIAs and 72, 99.6, 94.7 and 97.5% by EIAs. Discrepant results by CLIAs were more frequent than that by EIAs (9% vs. 6.3%); in those cases, PCR allowed for the accurate detection of toxigenic strains. Due to performance characteristics and testing comfort, CLIAs in combination with PCR represent a favourable option for the rapid laboratory C. difficile diagnostics.
Detection and differentiation of norovirus genogroups I and II from clinical stool specimens using real-time PCR
Ramanan P, Espy MJ, Khare R, Binnicker MJ. Diagn Microbiol Infect Dis 2017; 87(4): 325–327
A real-time RT-PCR assay was designed to detect and differentiate norovirus genogroups I (GI) and II (GII), with primers and probes targeting the nonstructural polyprotein gene. Stool samples (n=100) submitted for routine testing by the BioFire FilmArray® GI panel were also tested by the norovirus GI/GII real-time PCR assays. When compared to the FilmArray GI panel, the norovirus real-time PCR assay demonstrated a sensitivity of 77.5% (62/80) and specificity of 95% (19/20). Specimens yielding discordant results (n=19) were tested at two outside laboratories for adjudication. Following discordant resolution, the adjusted sensitivity and specificity of the norovirus real-time PCR assays were 96.9% (63/65) and 100% (35/35), respectively. These results suggest that the real-time PCR assays are able to accurately detect and differentiate norovirus GI/GII from clinical stool specimens. Furthermore, our report highlights a potential issue with the specificity of the BioFire FilmArray® norovirus assay, which warrants additional investigation.
Limited diagnostic value of a multiplexed gastrointestinal pathogen panel for the detection of adenovirus infection in an oncology patient population
McMillen T, Lee YJ, Kamboj M, Babady NE. J Clin Virol 2017; 94: 37–41
BACKGROUND: Diagnosis of adenovirus infections in transplant patients may be accomplished using either plasma or stool samples. IVD-cleared multiplexed gastrointestinal (GI) PCR panels offer an option for rapid testing of stool samples but most only target adenovirus (HAdV) types F40/41.
OBJECTIVES: Given the potential significance of a positive adenovirus test in an immunocompromised patient, we sought to determine the frequency of type 40/41 in our patient population and the utility of a readily available multiplexed, FDA-cleared GI Panel for the detection of adenovirus infections.
STUDY DESIGN: A total of 215 specimens from immunocompromised patients mostly with hematologic malignancy or transplant recipients were evaluated including 107 plasma samples, 85 stool samples and 23 respiratory samples. Genotyping was performed successfully on 122 specimens.
RESULTS: The most common type detected in all samples including stools was adenovirus C/2. In a subset of patients with multiple specimen types tested, similar types were detected in all samples.
CONCLUSIONS: Although adenovirus F40/41 is the most common enteric type, adenovirus C/2 was the most common type identified in stools and subsequently plasma samples of our patient population. Implementation of assays that have wide reactivity for most adenovirus types is essential for optimal diagnostic yield.
Synergistic effect of hyperglycemia and Helicobacter pylori infection status on colorectal adenoma risk
Hu KC, Wu MS, Chu CH, Wang HY, Lin SC, et al. J Clin Endocrinol Metab 2017; 102(8): 2744–2750
CONTEXT: Both Helicobacter pylori and type 2 diabetes mellitus are possible risk factors for colon adenoma.
OBJECTIVE: The purpose of this study was to assess the interaction between H. pylori and hyperglycemia status on the risk of colon adenoma.
DESIGN, SETTING, AND PARTICIPANTS: This was a cross-sectional, retrospective study conducted at the MacKay Memorial Hospital, Taiwan. The study included 3943 subjects aged >40 years undergoing bidirectional gastrointestinal endoscopy on the same day between July 2006 and June 2015. All subjects had a gastric biopsy specimen tested for H. pylori.
MAIN OUTCOME MEASURE: Colon adenoma with and without H. pylori infection at different hemoglobin A1c (HbA1c) levels.
RESULTS: The prevalence of colorectal adenomas in patients who were H. pylori-positive and H. pylori-negative was 37.3% and 27.29%, respectively. Multivariate logistic regression analysis identified male sex, age, body mass index, H. pylori infection, and HbA1c ≥6.5% as independent risk factors for adenoma; use of hypoglycemic agents decreased this risk. The prevalence of adenoma was increased with elevated HbA1c levels regardless of H. pylori status. The odds ratio (OR) for adenoma was 1.44 (95% confidence interval [CI], 1.20 to 1.73) if H. pylori was present or 1.68 (95% CI, 1.05 to 2.70) in patients who were H. pylori-negative but had HbA1c ≥7.0%. If both conditions were present, the OR was 4.79 (95% CI, 2.92 to 7.84). A 1% increase in HbA1c was associated with an increased prevalence of adenoma by 42.4% in H. pylori-positive subjects.
CONCLUSIONS: The combination of H. pylori infection and elevated HbA1c is associated with an increased risk of colon adenoma.
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