Beukenlaan 137
5616 VD Eindhoven
The Netherlands
+31 85064 55 82
info@clinlabint.com
PanGlobal Media is not responsible for any error or omission that might occur in the electronic display of product or company data.
Featured Articles
Looking at ANA testing from a different perspective
by James D. Peele, PhD The HEp-2 immunofluorescence assay (IFA) for ANA screening is excellent for ruling out many connective tissue diseases, but a positive result seldom translates into a clinically meaningful diagnosis. A new automated, efficient, enzyme immunoassay for ANA screening provides reliable, objective information that can be applied clinically with confidence.
Electronic alerts for acute kidney injury: the role of the laboratory
Acute kidney injury is a common and serious complication of many hospital admissions, yet there are often delays in recognizing its development. The laboratory can play a key role in ensuring large increases in serum creatinine do not go unnoticed so that deteriorating patients receive prompt medical attention.
by Nick Flynn
Introduction
Acute kidney injury (AKI) is a sudden decline in renal function, generally occurring over hours or days. AKI is increasingly recognized as a common healthcare problem associated with poor outcomes such as increased mortality and progression of chronic kidney disease [1], prolonged hospital stay and increased healthcare costs [2]. There is also evidence that management of patients with AKI is sometimes poor: in the UK, a National Confidential Enquiry into Patient Outcomes and Death (NCEPOD) report found severe deficiencies of care in a cohort of patients who died with a primary diagnosis of AKI [3]. For example, there was often a delay in recognizing post-admission AKI. This has prompted some hospitals to implement electronic alerts (e-alerts) to systematically detect and highlight cases of AKI. As current definitions of AKI are based mainly upon changes in serum creatinine, laboratories are well placed to implement these systems (Table 1) [4]. This review will briefly discuss options for e-alerts, some considerations for their implementation, and the evidence base for their use.
AKI e-alerts
The aim of AKI e-alert systems is to improve the outcomes of patients by facilitating earlier recognition and treatment of AKI. E-alerts may be triggered by a variety of different criteria, ranging from a single threshold creatinine value to full application of AKI diagnostic criteria. This may result in an automated comment being appended to the creatinine result, a phone call, email or text message to the requesting doctor, nephrologist or critical care outreach team, or a combination of the above. The intention is for the alert to prompt medical attention for these high-risk deteriorating patients, with a resulting improvement in patient outcomes (Fig. 1). The most successful e-alert systems are therefore likely to combine the alert with a clinical protocol for AKI management, and should be developed in collaboration with clinical colleagues.
Choosing alert criteria
Although a single threshold creatinine (for example, 300 µmol/L) is the simplest approach, this lacks both sensitivity and specificity for AKI. Creatinine may need to rise significantly before reaching the threshold, so the speed at which AKI is recognized may not be improved. In addition, depending on the population served by the laboratory, a large number of elevated creatinine results are likely to be from patients with stable chronic kidney disease, rather than AKI.
Accuracy can be improved by applying a ‘delta check’ to flag an absolute or percentage increase in creatinine, for example, a 75% increase in creatinine [5]. It is usually within the realms of most modern laboratory information management systems to offer one delta check for creatinine, and it is also sometimes possible to run multiple checks with different criteria. Finally, some systems aim to fully apply current definitions, such as those recommended by KDIGO (Table 1) [4].
Accurately estimating baseline creatinine is difficult
A problem faced both by simple delta checks and e-alerts based on AKI definitions is the difficulty in reliably estimating baseline creatinine. A system employing manual estimation of baseline by clinical biochemists at the Royal Derby Hospital has been shown to have good diagnostic accuracy for detection of AKI with a false negative rate of 0.2% and a false positive rate of 1.7% [6]. However, this approach is limited to normal working hours and many laboratories do not have the resources to replicate this labour intensive system. Instead, automatic surrogate estimation methods are used, such as the lowest, most recent or median creatinine value within a certain timeframe, such as the previous three months. Laboratories should be aware of the limitations of some of these estimation methods; for example, the lowest creatinine result has been shown to be a particularly poor estimate of baseline creatinine that can lead to high rates of potential AKI misclassification [7].
Should every case fulfilling AKI criteria be highlighted?
When choosing criteria for an e-alert system, it may seem sensible to use current definitions for AKI. However, there are arguments against this approach. The KDIGO definition of AKI relies on small changes in serum creatinine based on epidemiological studies which show that even these small increases are associated with an increase in mortality risk in large populations [2]. However, in many cases an increase of 0.3 mg/dl (≥26.5 µmol/L) is within the realms of normal biological variation, particularly amongst patients with chronic kidney disease. As an illustrative example, creatinine increased by between 69% and 129% after the consumption of 300 g of animal protein in healthy volunteers, even with creatinine measurement using a specific enzymatic method [8]. The limitations of the more widely used Jaffe method for serum creatinine are well known amongst laboratory professionals, and any of a wide range of non-creatinine chromogens may cause an increased result in the absence of renal disease. When KDIGO criteria are combined with a poor method of baseline estimation (lowest previous creatinine), the proportion of creatinine results causing an AKI e-alert can approach 10%; this is unlikely to be helpful. Strict application of current AKI definitions could therefore lead to annoyance and unresponsiveness amongst clinicians alerted to minor creatinine elevations, unnecessary interventions, anxiety for patients and families, and diversion of limited healthcare resources to a large and relatively low risk group. It is therefore important for laboratories to consider both local IT and resource capabilities and the relative benefit and harm of different criteria for e-alerts before implementation.
Evidence base
A small number of studies have investigated the effect of AKI e-alerts on clinician behaviour or patient outcomes. For example, a real-time alert of worsening AKI stage through a text message sent to the clinician’s telephone was found to increase the number of early therapeutic interventions in an ICU in Belgium [9]. There was also an increase in the proportion of patients who recovered their renal function within 8 hours after an alert indicating less severe AKI, but not amongst those with more severe AKI. There was no significant effect on renal replacement therapy, ICU length of stay, mortality, maximum creatinine or maximum AKI stage. Importantly, 9 out of 10 AKI alerts were based on urine volume criteria, so the applicability of these findings to creatinine based e-alerts is questionable.
Hospitals that have already implemented AKI e-alerts have noted improved outcomes following their introduction. For example, a hospital-wide e-alert system based on changes in serum creatinine at the Royal Derby Hospital, led to a progressive reduction in 30 day mortality over consecutive 6 month periods (23.7%, 20.8%, 20.8%, 19.5%, chi-square for trend P=0.006) [10]. This improvement in survival was maintained after adjustment for age, co-morbid conditions, severity of AKI, elective/non-elective admission and baseline renal function. However, the e-alert was introduced as part of a range of educational interventions so it is difficult to determine the contribution made by the e-alert component.
The evidence base for AKI e-alerts is therefore not strong, and would benefit from further studies to demonstrate that this approach can lead to measurable improvements in patient outcomes.
Conclusions
E-alerts represent an opportunity for the laboratory to assist in the early detection of acute kidney injury. This could improve the outcomes of patients with this life threatening condition. Aside from AKI, there are undoubtedly many other opportunities for the laboratory to optimize existing resources by helping clinicians to digest the large amount of laboratory data produced on a daily basis, to highlight trends and to ensure that important changes are recognized and acted upon. The laboratory can play a key role to ensure that these systems are implemented, that they are effective in selectively capturing a high risk population, and that evidence is gathered to justify their continued use.
References
1. Coca SG, et al. Long-term risk of mortality and other adverse outcomes after acute kidney injury: a systematic review and meta-analysis. Am J Kidney Dis. 2009; 53(6): 961–973.
2. Chertow GM, et al. Acute kidney injury, mortality, length of stay, and costs in hospitalized patients. J Am Soc Nephrol. 2005; 16: 3365–3370.
3. Stewart J, et al. Adding Insult to Injury: a review of the care of patients who died in hospital with a primary diagnosis of acute kidney injury (acute renal failure). A report by the National Confidential Enquiry into Patient Outcome and Death. London: NCEPOD, 2009. www.ncepod.org.uk/2009report1/Downloads/AKI_report.pdf
4. Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int. Suppl. 2012; 2: 1–138.
5. Thomas M, et al. The initial development and assessment of an automatic alert warning of acute kidney injury. Nephrol Dial Transplant 2011; 26: 2161–2168.
6. Selby N, et al. Use of electronic results reporting to diagnose and monitor aki in hospitalized patients. Clin J Am Soc Nephrol. 2012; 7: 533–540.
7. Siew ED, et al. Estimating baseline kidney function in hospitalized patients with impaired kidney function. Clin J Am Soc Nephrol. 2012; 7: 712-719.
8. Butani L, et al. Dietary protein significantly affects the serum creatinine concentration. Kidney Int. 2002; 61: 1907.
9. Colpaert K, et al. Impact of real-time electronic alerting of acute kidney injury on therapeutic intervention and progression of RIFLE class. Crit Care Med. 2012; 40: 1164–1170.
10. Kohle N, et al. Impact of a combined, hospital-wide improvement strategy on the outcomes of patients with acute kidney injury (AKI) [abstract]. Joint Congress of the British Transplantation Society & Renal Association, 2013. Bournemouth. Abstract O30. www.btsra2013.com/
The author
Nick Flynn, Pre-registration clinical scientist
Department of Clinical Biochemistry, University College London Hospitals, London, UK
E-mail: nick.flynn@nhs.net
NGAL as a biomarker of acute kidney injury
The diagnosis of acute kidney injury (AKI) is often hindered by the reliance on serum creatinine as a marker of kidney function, which can delay detection. Neutrophil gelatinase-associated lipocalin is a promising biomarker which increases within hours of kidney damage and could therefore improve the early diagnosis of AKI.
by Dr Ashley Garner
Clinical background
Acute kidney injury (AKI) is a common condition associated with significant morbidity and mortality. It is currently diagnosed using serum creatinine and urinary output as markers of kidney function, as defined in the recent KDIGO criteria [Fig. 1][1]. However, these are relatively late markers of AKI since they mainly reflect a decrease in glomerular filtration rate and the time required for serum creatinine to accumulate can delay diagnosis. Biomarkers that can detect structural injury to the kidney rather than a loss of function may allow better and earlier detection of AKI. Earlier diagnosis of AKI could facilitate earlier intervention, potentially reduce the risk of irreversible kidney damage and improve patient outcomes. Much research in recent years has therefore focused on the discovery of improved biomarkers for AKI and neutrophil gelatinase-associated lipocalin (NGAL) is one of the most promising candidates [2].
Pathophysiology of NGAL
NGAL is a small 25kDa protein which belongs to the superfamily of lipocalins. It is expressed in many cells including neutrophils, hepatocytes and renal tubular cells and is induced in response to pathological stimuli including infection, inflammation, ischemia and malignancy. NGAL has a functional role in the innate immune system as a bacteriostatic agent, depleting iron-binding siderophores and thereby preventing bacterial iron acquisition. The iron-binding properties of NGAL are also proposed to provide protection from oxidative stress. There is growing evidence that NGAL also acts as a growth factor in some tissues including renal epithelial cells where it modulates cell proliferation, differentiation and apoptosis and may provide protection against renal tubular damage in AKI [3].
Animal studies of AKI induced by ischemia or nephrotoxicity have shown that NGAL is one of the most upregulated proteins in the kidney and is detectable in the urine within 2–3 h. It has been reported that urine NGAL concentrations increase 25–100 fold and plasma NGAL increases 7–16 fold following AKI. Unlike serum creatinine, NGAL is not increased when there is impaired glomerular filtration without renal tubular damage, often termed ‘pre-renal’ uraemia.
Low plasma concentrations of NGAL are found in health as it is expressed at a low constant rate from various tissues. NGAL is then freely filtered at the kidney and the majority is reabsorbed in the proximal tubule, resulting in low NGAL concentrations in the urine. Following AKI, NGAL is greatly upregulated in the cells lining the ascending loop of Henle and collecting ducts of the kidney and is then excreted in the urine. The origin of the increase in plasma NGAL following AKI is less clear and there is evidence to suggest that NGAL expression is increased in other organs such as the lungs and liver following kidney injury.
Since NGAL can be produced by different tissues in response to various stimuli, it is not specific to AKI. Other common conditions that can cause elevated NGAL, and therefore complicate the interpretation of results, include sepsis, heart failure, chronic kidney disease (CKD), malignancy and urinary tract infections.
NGAL assays
Commercial CE marked assays are available for measuring NGAL in plasma, whole blood and urine. It is not clear from the literature whether any of these sample types are preferred or have better diagnostic performance but there are limiting factors for each that may require consideration. Plasma and whole blood samples are invasive and may be contaminated by haemolysis releasing NGAL from neutrophils. Urine NGAL may theoretically be more sensitive for AKI due to greater induction in renal tubular cells but can be falsely elevated in urinary tract infections due to leukocyturia and it is still unclear whether the NGAL should be corrected for urine concentration effects or whether this is unnecessary or even misleading in AKI. Although non-invasive, urine samples may be more difficult to obtain especially at specific time points or if the patient has reduced urine output.
NGAL exists in monomeric, dimeric and heterodimeric or complexed forms. It has been reported that the monomer is the predominant form produced by renal tubular cells and the homodimer is predominantly released by neutrophils. The relevance of these different forms of NGAL will depend on the extent to which NGAL assays detect them and the sample type used. Even though the monomer form may be most relevant for urine NGAL the origin of plasma NGAL in AKI is less clear and may therefore include the other forms. This variation in NGAL assays and sample types makes it difficult to directly compare study results and derive clinically relevant cut-off values. Standardization of NGAL assays using an internationally approved reference material would greatly improve this variation but this is not currently available and would require agreement on what forms of NGAL should be measured.
Research from large heterogeneous populations suggests that urine NGAL concentrations are dependent on gender, age and ethnicity. Biological variation for urine NGAL has also been reported to be as high as 84%. These factors will need to be taken into account when establishing reference intervals for NGAL although they may not be clinically significant if a cut-off value is used to diagnose AKI, especially if it greatly exceeds the expected reference intervals in health.
Clinical utility of NGAL in AKI
There is evidence that NGAL could be useful as an early diagnostic and prognostic biomarker for AKI. Many studies have demonstrated that NGAL rises 24–72 h before creatinine in patients with AKI and is associated with poorer outcomes. It is difficult to determine the diagnostic performance of NGAL for AKI in terms of clinical sensitivity and specificity however, due to the limitations of using serum creatinine as the gold standard comparator. For example, the rise in creatinine caused by pre-renal uraemia will not be associated with a raised NGAL. In addition, a multicentre pooled analysis of prospective studies has shown that patients who have raised NGAL without increases in serum creatinine are at increased risk of adverse outcomes and suggests these patients have a condition termed ‘subclinical AKI’ where there may be tubular damage without glomerular impairment [Fig. 2][4].
The majority of studies assessing NGAL testing in AKI have focused on specific patient populations at high risk of AKI: namely post-cardiac surgery, post contrast infusion, intensive care and emergency admissions.
The advantage of using NGAL in post-surgery or post-contrast patients is that the time of insult is known and therefore NGAL can be measured at set time points for the early detection of AKI and timely intervention. It is more difficult to determine the best application of NGAL in ICU patients in regard to the timing and frequency of tests and it is less clear whether earlier detection can improve outcomes in these patients frequently complicated by multi-organ failure. In the emergency admissions setting NGAL has fewer advantages over serum creatinine since early detection (within hours) is less likely to be applicable. Also NGAL, like creatinine, can be raised in CKD so may require multiple measurements to detect AKI but more patients are likely to have had a previous creatinine result than an NGAL result.
Although there is an abundance of observational studies showing that AKI can be detected earlier using NGAL compared to serum creatinine there is an absence of randomized clinical trials to demonstrate that using NGAL instead of current practice will improve patient outcomes or provide cost benefits. This is probably the biggest barrier to the adoption of NGAL testing in routine practice and better treatments and interventions may be required to overcome it. This would suggest that one of the most important roles for NGAL and earlier biomarkers of AKI is in the discovery and development of effective interventions and therapeutics.
Another consideration regarding interventions for AKI is that NGAL only detects renal tubular damage, it does not distinguish between different causes. However, effective treatments may require the underlying cause to be determined and therefore further biomarkers may be needed to differentiate between causative factors and indicate the most appropriate intervention.
Conclusion
A large number of clinical studies suggest that NGAL may provide an early diagnostic and prognostic biomarker for AKI. However, further randomized clinical trials comparing the use of NGAL to standard practice are required to show cost benefits or improvements in patient outcomes. It seems that even if biomarkers like NGAL enable us to detect AKI earlier, this alone may not be sufficient to improve patient care but hopefully they will facilitate the development of better interventions that will eventually lead to improved outcomes for patients with AKI.
References
1. Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int. Suppl. 2012; 2: 1–138.
2. ADQI Consensus on AKI Biomarkers and Cardiorenal Syndromes. Contrib Nephrol. Basel: Karger, 2013; 182: 13–29.
3. Schmidt-Ott KM, Mori K, Li JY, Kalandadze A, Cohen DJ, Devarajan P, Barasch J. Dual action of neutrophil gelatinase-associated lipocalin. J Am Soc Nephrol. 2007; 18: 407–413.
4. Haase M, Devarajan P, Haase-Fielitz A, Bellomo R, Cruz DN, Wagener G, Krawczeski CD, Koyner JL, Murray P, Zappitelli M, Goldstein SL, Makris K, Ronco C, Martensson J, Martling CR, Venge P, Siew E, Ware LB, Ikizler TA, Mertens PR. The outcome of neutrophil gelatinase-associated lipocalin-positive subclinical acute kidney injury: a multicenter pooled analysis of prospective studies. J Am Coll Cardiol. 2011; 57(17): 1752–1761.
The author
Ashley Garner PhD
Department of Blood Sciences,
Leeds Teaching Hospitals Trust, Leeds, UK
E-mail: Ashley.Garner@leedsth.nhs.uk
CytoBead Assays – A state of the art combination of cell-based immunofluorescence and microparticle technology for simultaneous screening and differentiation in autoimmune diagnostics
Autoimmune diseases affect approximately 5 % of the population of developed countries with an increasing incidence. Analysis of disease-associated autoantibodies (AAb) plays a significant role in the differential diagnosis thereof. Indirect immunofluorescence (IIF) has been established as the gold standard for AAb screening in particular for systemic rheumatic diseases. In the recommended two-tier approach for antibody serology, confirmatory testing by molecular assay techniques such as ELISA is required to confirm positive findings by screening using IIF. To cope with the constantly increasing demand for AAb testing, new efficient diagnostic approaches are required. Thus, a new generation of IIF assays have been developed to combine screening and confirmatory testing on one platform for the simultaneous detection of AAb by cell-based and bead-based assays in one reaction environment. The multiplex analysis of antineutrophil cytoplasmic antibodies (ANCA) for the differential diagnosis of vasculitides will be discussed as a first application of this novel approach.
by Dr. Christina Fritz, Mandy Sowa and Dirk Roggenbuck
ANCA-associated vasculitis
Vasculitis is an inflammation affecting blood vessel walls and resulting in their damage, fibrinoid necrosis, tissue ischemia and necrosis, and finally vessel rupture with bleeding into the surrounding tissue [1, 2]. Due to etiological factors, systemic vasculitis is differentiated into primary and secondary vasculitis. Primary systemic vasculitis of particularly small vessels often has an autoimmune pathogenesis accompanied by the occurrence of ANCA [3,5-8]. Those so called ANCA-associated systemic vasculitides (AASV) comprise microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA or Churg-Strauss syndrome) or granulomatosis with polyangiitis (GPA or Wegener’s granulomatosis)[1, 2, 4]. In contrast, secondary vasculitis occurs in 5 – 10 % of patients with rheumatoid arthritis or with other autoimmune diseases (e.g., systemic lupus erythematosus [SLE], Sjögren’s syndrome). In addition, vasculitis can occur in patients suffering from infections such as HIV or hepatitis C.
In general, an acute AASV generally requires immunosuppressive treatment with high doses of cortisone. In severe cases, cyclophosphamide is recommended. Once remission is achieved, methotrexate, azathioprin, cotrimoxazol, leflunomid or mucophenolate mofetil are used as maintenance therapy.
Diagnosis of ANCA-associated vasculitis
According to the international consensus statement for the assessment of ANCA, IIF on ethanol-fixed human neutrophils (ethN) is followed by confirmation with antigen-specific molecular immunoassays [6-8]. IIF reveals two ANCA patterns sub-classifying ANCAs into cytoplasmic ANCA (cANCA) and perinuclear ANCA (pANCA). Regarding the autoantigenic target of ANCA, c and pANCA are directed against proteinase 3 (PR3) and myeloperoxidase (MPO), respectively. A positive cANCA pattern confirmed by the presence of PR3-ANCA is pathognomonic for GPA[5], whereas a positive pANCA pattern confirmed by MPO-ANCA is decisive for MPA and EGPA. Furthermore, the corresponding ANCA titres are strongly associated with activity of disease in patients suffering from GPA and MPA.
As a matter of fact, IIF is currently the only technique to provide a single reaction environment for the combined screening and confirmation of ANCA. Simultaneous detection of c and pANCA along with PR3- and MPO-ANCA would overcome time-consuming single parameter detection by different techniques [10].
The use of multiplexing bead-based IIF assays for the simultaneous detection of single ANCA reactivities provides the ideal reaction environment to be combined with ethN-based ANCA testing. The corresponding principle is based on a covalent surface immobilization of MPO and PR3 on microbeads coded by size and fluorescence. The differentiation in size and/or intensity of a red fluorescence dye filling entirely each microbead population generates a novel reaction environment for parallel analyte analysis [11] (figure 1).
Combination of cell-based and microbead based ANCA assessment by CytoBead assay
The CytoBead assay is a unique combination of a conventional cell-based immunofluorescence assay with multiplexing microbead technology in one reaction environment. A newly designed microscopic glass slide with triple parted wells is employed to fix ethN in the middle compartment and PR3- as well as MPO-coated microbeads in the right-hand compartment of the slide (figure 2). Thus, anti-PR3 antibody positive sera show a positive cytoplasmic fluorescence on ethN and a green fluorescence halo on the surface of PR3-coated microbeads (9 µm). In contrast, anti-MPO antibody positive sera demonstrate a perinuclear fluorescence pattern on the immobilized ethN and a fluorescence halo on the surface of MPO-coated microbeads (15 µm) (figure 2). A reference microbead population (12 µm) is integrated for particle differentiation. This assay set offers the possibility of classical evaluation by a simple fluorescence microscope as well as automated analysis by interpretation systems like the AKLIDES®.
A recent clinical study with classical ANCA testing revealed a relative sensitivity and specificity of 98 % and 99.2 % for the novel CytoBead ANCA assay, respectively. Remarkably, the CytoBead ANCA assay showed a better discrimination of GPA and MPA patients in contrast to the classical anti-MPO and anti-PR3 ELISA. The detected cut-off values were determined on the basis of fluorescence intensity given in arbitrary units [AU] (personal communication).
Conclusion and future perspectives
The increasing demand for cost-effective autoimmune diagnostics requires new multiplexing technologies combining screening and confirmatory testing in one reaction environment. Thus, the novel CytoBead technology is a promising opportunity to accomplish this goal as demonstrated for the comprehensive assessment of ANCA. Automated digital immunofluorescence employed by recently established novel diagnostic interpretation system solutions such as Aklides even offers quantification and standardization of ANCA detection. The CytoBead technology provides an ideal reaction environment for the multiplexing of antinuclear antibody assessment and the simultaneous detection of celiac disease-specific antibodies.
References
1. Watt RA, Scott DG. Recent advances in classification and assessment of vasculitis. Best Pract Res Clin Rheumatol. 2009; 23: 429-443
2. Jeanette JC, Falk RJ. Small-vessel vasculitis. N Eng J Med. 1997; 337: 1512-23
3. Gross WL, Trabant A, Reinhold-Keller E. Diagnosis and evaluation of vasculitis. Rheumatology (Oxford). 2000; 39: 245-52
4. Waller R, Ahmed A, Patel I, Luqami R. Update on the classification of vasculitis. Best Pract Res Clin Rheumatol. 2013; 27: 3-17
5. Bosch X, Guilabert A, Font J: Antineutrophil cytoplasmic antibodies. Lancet 2006, 368:404-18
6. Jennette JC, Falk RJ, Bacon PA, Basu N, Ferrario F, Flores-Suarez LF, Gross WL, Guillevin L, Hagen EC, Hoffman GS, Jayne DR, Kallenberg CG, Lamprecht P, Langford CA, Lugmani RA, Mahr AD, Matteson EL, Merkel PA, Ozen S, Pusey CD, Rasmussen N, Rees AJ, Scott DG, Specks U, Stone JH, Takahashi K, Watts RA: 2012 revised International Chapel Hill Consensus Conference Nomenclature of Vasculitis. Arthritis Rheum. 2013, 65:1-11
7. Jennette JC, Falk RJ, Andrassy K, Bacon PA, Churg J, Gross WL, Hagen EC, Hoffman GS, Hunder GG, Kallenberg CG: Nomenclature of systemic vasculitides. Proposal of an international consensus conference. Arthritis Rheum 1994, 37:187-92
8. Savige JF, Gillis DF, Benson E, Davies DF, Esnault VF, Falk RJ, Hagen EC, Jayne D, Jennette JC, Paspaliaris B, Pollock W, Pusey C, Savage CO, Silvestrini R, van der Woude F, Wieslander J, Wiik A: International Consensus Statement on Testing and Reporting of Antineutrophil Cytoplasmic Antibodies (ANCA). Am J Clin Pathol 1999, 111:507-13
9. Merkel PA, Polisson RP, Chang Y, Skates SJ, Niles JL: Prevalence of antineutrophil cytoplasmic antibodies in a large inception cohort of patients with connective tissue disease. Ann. Intern. Med. 1997, 126;866
10. Choi HK, Liu S, Merkel, PA, Colditz GA, Niles Jl: Diagnostic performance of antineutrophil cytoplasmic antibody tests for idiopathic vasculitides: metaanalysis with a focus on antimyeloperoxidase antibodies. J. Rheumatol. 2001, 28:1584
11. Grossmann K, Roggenbuck D, Schröder C, Conrad K, Schierack P, Sack U: Multiplex Assessment of Non-Organ-Specific Autoantibodies with a Novel Microbead-Based Immunoassay. 2011, Cytometry Part A! 79A: 118”125
Author
Dr. Christina Fritz*, Mandy Sowa and Dirk Roggenbuck
Medipan GmbH, Ludwig-Erhard-Ring 3,
15827 Dahlewitz,
Germany
*Corresponding author
E-mail: c.fritz@medipan.de
