In 2013, the National Institute for Health and Care Excellence (NICE) published guidelines recommending the use of fecal calprotectin as a screening test for differentiating between inflammatory bowel disease and irritable bowel syndrome. Since then, despite a relatively slow uptake with only a few laboratories offering the test, fecal calprotectin has garnered much interest with more hospitals incorporating it into their pathology services. Therefore, the question of how well primary care is using the service arises. This, along with a brief historical context of inflammatory bowel disease and its diagnosis together with implications of calprotectin testing are discussed here.
by Dr Benjamin Palmer, Dr Wisam Jafar and Steven McCann
Historical context
Inflammatory bowel disease (IBD) is a term used to describe two relapsing chronic gastrointestinal disorders: ulcerative colitis (UC) and Crohn’s disease (CD). Both cause considerable morbidity amongst young patients in whom they occur more frequently [1]. With an estimated prevalence of 2.5–3.0 million people affected in Europe the incidence of IBD is increasing [1]. Although the etiology of IBD is unknown several theories have been put forward the most important and frequently cited elements being: gut microbiota; genetic pre-disposition; environment and immune dysregulation [2]. The two main types of IBD seen in the clinical setting are UC and CD: definitive diagnosis and confirmation is provided by endoscopy and histology. However, in 5% of cases a definitive diagnosis cannot be established: in such cases patients are diagnosed with inflammatory bowel disease unclassified (IBDU) [3, 4].
The gastrointestinal tract is colonized by a large number of diverse bacteria living in symbiosis with their host (microbiota) [5]. Disruption to the diversity and quality of the gut microbiota (dysbiosis) is now implicated in the pathogenesis of both UC and CD [2, 5, 6]. Other important participants are cytokines: as their release causes intestinal inflammation they have been implicated in some of the clinical symptoms such as diarrhea [7–9].
Historically, the two types of IBD were differentiated by the different cytokines and mature CD4+ T helper (Th) cells found elevated in tissue biopsies. UC was characterized by elevated levels of Th2 cells and interleukin (IL)-4, -5, -10 and -13 cytokines, whereas CD was defined by high levels of Th1 cells and the interferon gamma (IFNγ) cytokine [3]. However, new emerging information suggests that it is not as cut and dried as this: emphasis has now shifted towards such pathways as IL-23/IL-17 activation of more pathogenic Th17 cells playing a more significant role in the pathophysiology of not just IBD but other inflammatory diseases [10].
Complicating the clinical scenario is the high prevalence (around 10−20% of the UK population) of an unrelated functional bowel disorder called irritable bowel syndrome (IBS): the true prevalence is thought to be higher as it is suspected that many people may not seek medical advice [11]. Although it does not cause serious morbidities, IBS manifests with symptoms similar to those of IBD, making diagnosis difficult. Unlike IBD, it is not associated with inflammation and, hence, this provides a means of making a differential diagnosis.
Until recently, the diagnosis of IBD was made by clinical evaluation and a combination of biochemical and mainly endoscopic investigations that often involved repeat consultations and testing [3]. This, taken together with an ageing population, an increased public awareness of bowel cancer and the introduction of national screening campaigns has led to increased service demands in endoscopy. The fact that fecal markers, such as calprotectin, are secreted by inflamed intestinal mucosa has led to the development of laboratory assays that can detect gastrointestinal inflammation. It was because of these challenges and recent developments that led the National Institute for Health and Care Excellence (NICE) to publish guidelines on the use of fecal calprotectin in differentiating IBD from IBS in adults provided cancer is not suspected and that local reporting guidelines along with appropriate quality assurance procedures are in place [12]. A cut-off of 50 μg/g is recommended in which all patients with a calprotectin level ≥50 μg/g may be suggestive of IBD and should be referred to Gastroenterology, whereas a calprotectin level <50 μg/g is unlikely to be caused by IBD and should, therefore, be managed with a presumptive diagnosis of IBS [12]. One key study used by NICE in recommending this threshold was carried out by Tibble et al. in which 602 outpatients with lower gastrointestinal tract symptom were included [13]. In this study the authors clearly demonstrated that the IBD group of patients differed significantly (P=0.001–<0.0001) from the IBS group of patients and that a cut-off level of 10 mg/L (equivalent to 50 μg/g) provided optimal diagnostic performance [13]. However, the cut-off level of any test is dependent on the method used and, therefore, each laboratory should establish their method-specific cut-off level [12].
IBD pathway and audit outcome
Following the recommendations of NICE, fecal calprotectin testing was incorporated into the pathology services at Stepping Hill hospital on 1 November 2014. The test is available for patients from primary care between 20 and 40 years of age who are presenting with abdominal pain or discomfort, bloating or altered bowel habits for 6 months or longer. Patients with red flag symptoms (anemia, abdominal mass, gastrointestinal infection, rectal bleeding, unexplained weight loss or a family history of ovarian or bowel cancer) should be referred directly to Gastroenterology (Fig. 1).
If the calprotectin test is negative the patient should be managed by primary care with a presumptive diagnosis of IBS; if the test is positive the patient should be referred to Gastroenterology. Then in 2016 a 1-year retrospective audit was carried out with the aim of determining how well primary care was adhering to the clinical pathway [14]. In order to achieve this, a questionnaire was designed and sent to all primary care surgeries in the catchment area for each patient who received calprotectin testing (n=587): the responses (n=217) to these questionnaires were then compared to the IBD pathway [14].
The outcome of this audit revealed that most areas of the IBD pathway were not being adhered to and, therefore, GP re-education and training was needed; a similar finding to another hospital [10]. The worst area of non-conformance was to ensure that patients had had signs/symptoms for at least 6 months: 69% of requests were not compliant [14]. Exclusion of gastrointestinal infection was second (63%), followed by ensuring age was 20–40 years (48%) [14]. Of the 216 questionnaires returned, 35% of patients had had red flag signs/symptoms at the time of the request [14]. Alarmingly, rectal bleeding was the most frequently encountered, followed by anemia, unexplained weight loss and a family history of bowel/ovarian cancer [14]. None of the patients had abdominal mass [14]. Conversely, high compliance was observed for the withdrawal of non-steroidal inflammatory drugs (NSAIDs) and antibiotics before testing [14]. Overall, only 24 requests (11%) were fully compliant for all criteria of the IBD clinical pathway [14].
Patient/clinician considerations
Unlike other fecal markers such as elastase, calprotectin is much less stable (up to 3 days at room temperature) and, therefore, it is important that patient samples are sent to the laboratory within 72 hours of collection [16]. It is still the case that samples are received by the laboratory with no date or time of collection and these are consequently rejected for analysis. Considering that calprotectin is elevated in gastrointestinal infection, in order for the test to be of clinical use, it is imperative that this is excluded.
The age restriction imposed on calprotectin testing is important and is based on the fact that IBS is more common in younger adults, that the prevalence of IBS decreases with increasing age and that new onset of symptoms after 50 years is uncommon [11, 17]. By focusing on this age group a large number of patients who do not require diagnostic testing will be excluded and, therefore, they will not add to the delay that current IBD sufferers face in receiving a colonoscopy.
Patients >40 years of age should be referred to Gastroenterology without delay, as the risk of developing colorectal cancer increases with age: colorectal cancer is the third most commonly diagnosed cancer in the UK and one of the major complications of IBD [18].
Since IBD is a relapsing disease the clinician should be aware that screening results from some patients with IBD may be negative, particularly if the disease is in a period of remittance and, therefore, the presentation of the patient, not the test result, should be the ultimate deciding factor over whether to refer. Finally, underpinning this is the need for local laboratories to determine their own method-specific cut-off values using evidence-based medicine. As with all screening tests the aim should be to optimize the test’s ability to exclude disease (IBS) so that fewer patients without disease are referred.
References
1. Trbojevic Akmacic I, Ventham NT, Theodoratou E, Vuckovic F, Kennedy NA, Krištic J, Nimmo ER, Kalla R, Drummond H, et al. Inflammatory bowel disease associates with proinflammatory potenial of the immunoglobulin G glycome. Inflamm Bowel Dis 2015; 21: 1237–1247.
2. de Souza HS, Fiocchi C. Immunopathogenesis of IBD: current state of the art. Nat Rev Gastroenterol Hepatol 2016; 186: 13–27.
3. Odze R. Diagnostic problems and advances in inflammatory bowel disease. Mod Pathol 2003; 16(4): 347–358.
4. Magro F, Giochetti P, Eliakim R, Ardissone S, Armuzzi A, Barreiro-de Acosta M, Burisch J, Gecse KB, Hart AL, et al. Third European evidence-based consensus on diagnosis and management of ulcerative colitis. Part1: definitions, diagnosis, extra-intestinal manifestations, pregnancy, cancer surveillance, surgery and ileo-anal pouch disorders. J Crohns Colitis 2017; 11(6): 649–670.
5. Salim SY, Söderholm JD. Importance of disrupted intestinal barrier in inflammatory diseases. Inflamm Bowel Dis 2011; 17(1): 362–381.
6. Ni J, Wu GD, Alenberg L, Tomov VT. Gut microbiota and IBD: causation or correlation? Nat Rev Gastroenterol Hepatol 2017; 14(10): 573–584.
7. Neurath MF. Cytokines in inflammatory bowel disease. Nat Rev Immunol 2014; 14(5): 329–342.
8. Műzes G, Molnár B, Tulassay Z, Sipos F. Changes of the cytokine profile in inflammatory bowel diseases. World J Gastroenterol 2012; 18(41): 5848–5861.
9. Ohama T, Hori M, Sato K, Ozaki H, Karaki H. Chronic treatment with interleukin-1β attenuates contractions by decreasing the activities of CPI-17 and MYPT-1 in intestinal smooth muscle. J Biol Chem 2003; 278(49): 48794–48804.
10. Iwakura Y, Ishigame H. The IL-23/IL-17 axis in inflammation. J Clin Invest 2006; 116(5): 1218–1222.
11. National Institute for Health and Care Excellence (NICE). Irritable bowel syndrome in adults: diagnosis and management of irritable bowel syndrome in primary care. NICE Clinical Guideline 61, 2008 (https://www.nice.org.uk/guidance/cg61).
12. NICE. Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel. NICE Diagnostics Guidance 11, 2013 (https://www.nice.org.uk/guidance/dg11).
13. Tibble J, Teahon K, Thjodleifsson B, Roseth A, Sigthorsson G, Bridger S, Foster R, Sherwood R, Fagerhol M, Bjarnason I. A simple method for assessing intestinal inflammation in Crohn’s disease. Gut 2000; 47: 506–513.
14. Palmer B, McCann S. A one year retrospective audit on calprotectin: how well is primary care adhering to the pathway for inflammatory bowel disease. Poster presented at Focus 2017, the Association of Clinical Biochemistry national annual meeting.
15. Turvill J. Evaluation of guidelines for the use of faecal calprotectin testing in primary care. NICE 2015. (https://www.nice.org.uk/sharedlearning/evaluation-of-guidelines-for-the-use-of-faecal-calprotectin-testing-in-primary-care).
16. Tøn H1, Brandsnes, Dale S, Holtlund J, Skuibina E, Schjønsby H, Johne B. Improved assay for faecal calprotectin. Clin Chim Acta 2000; 292: 41–54.
17. Halland M, Saito YA. Irritable syndrome: new and emerging treatments. BMJ 2015; 350: h1622.
18. Adelstein B, Macaskill P, Chan SF, Katelaris PH, Irwig L. Most bowel cancer symptoms do not indicate colorectal cancer and polyps: a systematic review. BMC gastroenterol 2011; 11: 65–74.
The authors
Benjamin Palmer*1 PhD, MRSC; Wisam Jafar2 MBChB, MRCP(gastro), MSc, MA, FRCP; Steven McCann2 MSc, FRCPath
1Betsi Cadwaladr Health Board, Glan Clwyd Hospital, Rhyl, Denbighshire, Wales, UK
2Stockport NHS Foundation Trust, Stockport, Cheshire, UK
*Corresponding author
E-mail: Ben.palmer@wales.nhs.uk
RESIST – get precise identifictaion of your CPO
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, /in Featured Articles /by 3wmediaGenomic tracking of MRSA outbreaks could help infection control
, /in Featured Articles /by 3wmediaHospital-acquired infections (HAIs) today rank among the major causes of death and morbidity in hospitalized patients and are estimated to be responsible for 175,000 deaths per year in industrialized countries. HAIs have been growing exponentially worldwide since the 1980s primarily because of the indiscriminate use of antibiotics which have triggered the growth of multidrug resistant bacterial strains – also known as superbugs – and the transmission of such strains between patients, as well as between patients and hospital staff and vice versa. Methicillin-resistant Staphylococcus aureus (MRSA) is a superbug that is resistant to several widely used antibiotics. In the general community, MRSA mostly causes skin infection, is spread by skin-to-skin contact and, if left untreated, can also get deeper into the body, causing potentially life-threatening infections. It is generally estimated that about 3 percent of the population chronically carries MRSA. However, in a healthcare setting such as a hospital or nursing home, MRSA infection is more frequent and often more severe, leading to pneumonia, surgical site infections, bloodstream infections and possibly sepsis. The risk factors are indeed much higher in hospitals because of the increased vulnerability of some patients (the elderly and those with weakened immune systems) and because of the multiple potential pathways for MRSA entry into the body provided by wounds (including surgical wounds), burns as well as feeding tubes, intravenous lines or urinary catheters. MRSA is also prevalent in nursing homes where healthy carriers have the opportunity to spread it among the resident population and staff.
A very recent study, published in the October 25 edition of Science Translational Medicine, used genomic sequencing technology for the genomic surveillance of MRSA in the East of England. A team at the Wellcome Trust Sanger Institute sequenced the genetic code of every single MRSA-positive sample processed over a 12-month period by a routine clinical microbiology lab receiving samples from three hospitals and 75 general practitioner practices. Samples from 1465 people were analysed, revealing a total of 173 transmission clusters involving 598 people and ranging from outbreaks affecting two patients up to 44. These findings shed some new light on MRSA transmission within and between hospitals and the community and could pave the way for more targeted, efficient and effective infection control practices. While genomic surveillance of MRSA cannot by itself prevent an outbreak from occurring, it can certainly help to reduce the numbers of infected people. The cost-effectiveness of implementing this strategy needs to be carefully evaluated. Although the whole genome of a bacterium can now be sequenced for around 140€, this might still prove too much for many healthcare systems.
Is a celiac screen in a ‘tired all the time’ test profile of any value?
, /in Autoimmunity & Allergy, Featured Articles /by 3wmediaby L. Hughes, Dr A. Ballantyne, Dr C. Ford, Dr A. Ekbote and Prof. R. Gama Celiac disease (CD) is a common autoimmune gastrointestinal disease. Several serological tests are available to screen for CD. Since CD can present with fatigue, serological screening was incorporated into a ‘tired all the time’ testing profile available to general […]
Evaluation of a highly automated fecal calprotectin assay for the differential diagnosis of IBD or IBS
, /in Featured Articles /by 3wmediaFecal calprotectin is an effective biomarker in the differential diagnosis of inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS). Since the National Institute for Health and Care Excellence (NICE) recommended its use there has been a significant increase in demand for analysis. New methods on mainline chemistry analysers can be implemented in response to the increase in workload.
by Sally Willett, Pamela Bowe, Frankie Leslie and Wayne Bradbury
Introduction
Chronic abdominal pain with diarrhea or constipation are common presenting symptoms in general practice. The differential diagnosis in this patient population is varied, but includes irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD).
IBS is a chronic, relapsing and often lifelong disorder associated with disordered defecation and abdominal distention. It is not associated with any distinctive pathology and although it is troublesome for the patient it is not associated with any serious comorbidity. IBS is a relatively common diagnosis with a prevalence of 10–20% in the general population [1].
IBD is a much more serious condition, associated with a high morbidity. The term IBD includes Crohn’s disease and ulcerative colitis, conditions in which gastrointestinal inflammation can lead to major complications. Patients may require surgery and are at increased risk of colorectal cancer. Evolving treatment options, including novel drugs and surgery, aim to secure and maintain remission [2].
It is important to distinguish IBD from non-IBD, such as IBS, so that conditions can be appropriately managed and monitored. Endoscopy with histological examination of biopsy samples remains the gold standard in differentiating IBD and IBS, but is very expensive, time consuming and invasive. Conventional diagnostic testing included markers of inflammation including C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). However, these markers cannot localize inflammation to the gut. There has been intensive research into fecal biomarkers, specific for gastrointestinal inflammation over the last decade.
Calprotectin is a small calcium binding protein which contributes ~60% of the protein content of the cytosol in neutrophils [3]. During the intestinal inflammation observed in patients with IBD neutrophils migrate to the intestinal mucosa. As the inflammatory process damages the mucosal architecture the neutrophils are shed into the lumen and calprotectin is detectable in the feces. A raised fecal calprotectin concentration (>50 µg/g) has been shown to have a good diagnostic sensitivity and specificity for the detection of IBD [4].
Analytical methods for the detection of calprotectin in feces have evolved since the original enzyme-linked immunosorbent assay (ELISA) method was described in 1992 [5]. Commercial immunoassays are now available and quantitative lateral flow immunochomatographic point-of-care tests have been marketed to generate rapid results in the clinic setting. Many laboratories still use ELISA technology to analyse fecal samples for calprotectin. Such analysis is relatively labour intensive and often fecal extracts are run in duplicate at increased cost.
Since the National Institute for Health and Care Excellence (NICE) recommended the use of fecal calprotectin in primary care [2], there has been a significant increase in demand for this test. We investigated the performance of the new BÜHLMANN fCALTM turbo method which is CE marked for use on a number of mainline chemistry analysers. Implementation of this method has the potential to streamline analysis, relieving staff time and reducing cost.
Method
The BÜHLMANN fCALTM turbo particle enhanced turbidimetric immunoassay (PETIA) method on the Roche Cobas 6000 (c501) was compared to the BÜHLMANN Calprotectin ELISA method on the Dynex DS2. The study was performed within the Blood Sciences Department at North Cumbria University Hospitals.
The PETIA method uses polystyrene nanoparticles coated with specific antibodies to bind calprotectin in fecal extracts. Calprotectin in the sample mediates immune-particle agglutination and the resultant increase in turbidity is quantified by optical density.
Fecal samples were extracted using the BÜHLMANN CALEX® extraction device prior to analysis on both methods. Fifty-eight patient samples were analysed and results compared using regression analysis. Intra-assay precision was determined using 10 replicates of patient samples and inter-assay precision was calculated using 17 replicates of internal quality control material. NEQAS samples were analysed and bias relative to the all laboratory trimmed mean (ALTM) was assessed.
Results and discussion
Comparison of patient results showed good correlation (R2=0.97) consistent with previous studies [6, 7]. Regression analysis produced the following equation:
fCALTM turbo = (1.14×DS2 result)−23.42
The fCALTM turbo method demonstrated a negative bias at concentrations <100 µg/g and a positive bias at higher concentrations when compared with the ELISA method (Fig. 1), which has also been observed by De Sloovere et al. [6]. The positive bias observed at higher concentrations is accounted for in local guidelines. Since the initial evaluation a field safety notice (FSN) was distributed informing users that a positive bias of 15.6% was observed using the BÜHLMANN CALEX® extraction devices. This has subsequently been corrected with the CALEX® Cap “N” devices. After the introduction of the revised extraction devices external quality assurance (EQA) results have improved, and local results show a mean bias of 54 µg/g from the NEQAS ALTM (Fig. 2). A commutable reference material for calprotectin is required to define analytical accuracy in the future.
Intra-assay precision, as determined by percent coefficient of variation (%CV), was 3.1% and 1.3% at concentrations of 48 µg/g and 247 µg/g respectively (n=10). Inter-assay precision was 3.3% at 73 µg/g and 1.1% at 247 µg/g (n=17). This is consistent with De Sloovere et al. who demonstrated %CVs of ~3% using the fCAL turbo method [6]. Since running the method routinely the internal quality control data shows a running %CV of 4.5% at 75 µg/g and 2.6% at 245 µg/g (n=23).
Historically, fecal samples required weighing and diluting in extraction buffer before analysis, which was very labour intensive and prone to error. The introduction of extraction devices has simplified the pre-analytical steps significantly. The introduction of the PETIA method into our laboratory has further simplified analysis and reduced staff time, as the fecal extracts are loaded directly onto the Cobas 6000 in barcoded CALEX tubes. The PETIA method has a large analytical range (20–1800 µg/g feces) reducing the requirement for costly repeat analysis on dilution. Although the ELISA method favours batch analysis, the PETIA method is suitable for random access testing, improving assay turnaround times. An additional wash step is implemented to eliminate carry over between fecal and blood samples.
Conclusion
It is important to accurately differentiate IBD from IBS so that appropriate patient care pathways can be instigated. The methodologies available for the quantification of fecal calprotectin have evolved significantly over the last decade. The BÜHLMANN fCALTM turbo PETIA method on the Roche Cobas 6000 (c501) demonstrated acceptable performance and is suitable for routine use within a diagnostic laboratory.
References
1. National Institute for Health and Clinical Excellence (NICE). Irritable bowel syndrome in adults: diagnosis and management. NICE clinical guideline 61, 2008.
2. NICE. Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel. NICE diagnostic guideline 11, 2013.
3. Fagerhol M, Dale I, Andersson T. A radioimmunoassay for a granulocyte protein as a marker in studies on the turnover of such cells. Bull Eur Physiopathol Respir 1980; 16(Suppl): 273–282.
4. Walsham N and Sherwood R. Fecal calprotectin in inflammatory bowel disease. Clin Exp Gastroenterol 2016; 9: 21–29.
5. Roseth AG, Fagerhol MK, Aadland E, Schiønsby H. Assessment of the neutrophil dominating protein calprotectin in feces. A methodologic study. Scand J Gastroenterol 1992; 27: 793–798.
6. De Sloovere M, De Smet D, Baert F, Debrabandere J, Vanpoucke HJM. Analytical and diagnostic performance of two automated fecal calprotectin immunoassays for detection of IBD. Clin Chem Lab Med 2017; 28: 1435–1446.
7. Nilsen T, Sunde K, Hansson L, Havelka AM, Larsson A. A novel turbidimetric immunoassay for fecal calprotectin optimized for routine chemistry analysers. J Clin Lab Anal Analysis 2017; 31: 1–6.
The authors
Sally Willett FRCPath, Pamela Bowe* MSc, Frankie Leslie BSc, Wayne Bradbury FRCPath
Blood Sciences, North Cumbria University Hospitals NHS Trust, Cumberland Infirmary, Carlisle, UK
*Corresponding author
E-mail: Pamela.Bowe@ncuh.nhs.uk
Calprotectin use in primary care. Are testing criteria being followed?
, /in Featured Articles /by 3wmediaIn 2013, the National Institute for Health and Care Excellence (NICE) published guidelines recommending the use of fecal calprotectin as a screening test for differentiating between inflammatory bowel disease and irritable bowel syndrome. Since then, despite a relatively slow uptake with only a few laboratories offering the test, fecal calprotectin has garnered much interest with more hospitals incorporating it into their pathology services. Therefore, the question of how well primary care is using the service arises. This, along with a brief historical context of inflammatory bowel disease and its diagnosis together with implications of calprotectin testing are discussed here.
by Dr Benjamin Palmer, Dr Wisam Jafar and Steven McCann
Historical context
Inflammatory bowel disease (IBD) is a term used to describe two relapsing chronic gastrointestinal disorders: ulcerative colitis (UC) and Crohn’s disease (CD). Both cause considerable morbidity amongst young patients in whom they occur more frequently [1]. With an estimated prevalence of 2.5–3.0 million people affected in Europe the incidence of IBD is increasing [1]. Although the etiology of IBD is unknown several theories have been put forward the most important and frequently cited elements being: gut microbiota; genetic pre-disposition; environment and immune dysregulation [2]. The two main types of IBD seen in the clinical setting are UC and CD: definitive diagnosis and confirmation is provided by endoscopy and histology. However, in 5% of cases a definitive diagnosis cannot be established: in such cases patients are diagnosed with inflammatory bowel disease unclassified (IBDU) [3, 4].
The gastrointestinal tract is colonized by a large number of diverse bacteria living in symbiosis with their host (microbiota) [5]. Disruption to the diversity and quality of the gut microbiota (dysbiosis) is now implicated in the pathogenesis of both UC and CD [2, 5, 6]. Other important participants are cytokines: as their release causes intestinal inflammation they have been implicated in some of the clinical symptoms such as diarrhea [7–9].
Historically, the two types of IBD were differentiated by the different cytokines and mature CD4+ T helper (Th) cells found elevated in tissue biopsies. UC was characterized by elevated levels of Th2 cells and interleukin (IL)-4, -5, -10 and -13 cytokines, whereas CD was defined by high levels of Th1 cells and the interferon gamma (IFNγ) cytokine [3]. However, new emerging information suggests that it is not as cut and dried as this: emphasis has now shifted towards such pathways as IL-23/IL-17 activation of more pathogenic Th17 cells playing a more significant role in the pathophysiology of not just IBD but other inflammatory diseases [10].
Complicating the clinical scenario is the high prevalence (around 10−20% of the UK population) of an unrelated functional bowel disorder called irritable bowel syndrome (IBS): the true prevalence is thought to be higher as it is suspected that many people may not seek medical advice [11]. Although it does not cause serious morbidities, IBS manifests with symptoms similar to those of IBD, making diagnosis difficult. Unlike IBD, it is not associated with inflammation and, hence, this provides a means of making a differential diagnosis.
Until recently, the diagnosis of IBD was made by clinical evaluation and a combination of biochemical and mainly endoscopic investigations that often involved repeat consultations and testing [3]. This, taken together with an ageing population, an increased public awareness of bowel cancer and the introduction of national screening campaigns has led to increased service demands in endoscopy. The fact that fecal markers, such as calprotectin, are secreted by inflamed intestinal mucosa has led to the development of laboratory assays that can detect gastrointestinal inflammation. It was because of these challenges and recent developments that led the National Institute for Health and Care Excellence (NICE) to publish guidelines on the use of fecal calprotectin in differentiating IBD from IBS in adults provided cancer is not suspected and that local reporting guidelines along with appropriate quality assurance procedures are in place [12]. A cut-off of 50 μg/g is recommended in which all patients with a calprotectin level ≥50 μg/g may be suggestive of IBD and should be referred to Gastroenterology, whereas a calprotectin level <50 μg/g is unlikely to be caused by IBD and should, therefore, be managed with a presumptive diagnosis of IBS [12]. One key study used by NICE in recommending this threshold was carried out by Tibble et al. in which 602 outpatients with lower gastrointestinal tract symptom were included [13]. In this study the authors clearly demonstrated that the IBD group of patients differed significantly (P=0.001–<0.0001) from the IBS group of patients and that a cut-off level of 10 mg/L (equivalent to 50 μg/g) provided optimal diagnostic performance [13]. However, the cut-off level of any test is dependent on the method used and, therefore, each laboratory should establish their method-specific cut-off level [12].
IBD pathway and audit outcome
Following the recommendations of NICE, fecal calprotectin testing was incorporated into the pathology services at Stepping Hill hospital on 1 November 2014. The test is available for patients from primary care between 20 and 40 years of age who are presenting with abdominal pain or discomfort, bloating or altered bowel habits for 6 months or longer. Patients with red flag symptoms (anemia, abdominal mass, gastrointestinal infection, rectal bleeding, unexplained weight loss or a family history of ovarian or bowel cancer) should be referred directly to Gastroenterology (Fig. 1).
If the calprotectin test is negative the patient should be managed by primary care with a presumptive diagnosis of IBS; if the test is positive the patient should be referred to Gastroenterology. Then in 2016 a 1-year retrospective audit was carried out with the aim of determining how well primary care was adhering to the clinical pathway [14]. In order to achieve this, a questionnaire was designed and sent to all primary care surgeries in the catchment area for each patient who received calprotectin testing (n=587): the responses (n=217) to these questionnaires were then compared to the IBD pathway [14].
The outcome of this audit revealed that most areas of the IBD pathway were not being adhered to and, therefore, GP re-education and training was needed; a similar finding to another hospital [10]. The worst area of non-conformance was to ensure that patients had had signs/symptoms for at least 6 months: 69% of requests were not compliant [14]. Exclusion of gastrointestinal infection was second (63%), followed by ensuring age was 20–40 years (48%) [14]. Of the 216 questionnaires returned, 35% of patients had had red flag signs/symptoms at the time of the request [14]. Alarmingly, rectal bleeding was the most frequently encountered, followed by anemia, unexplained weight loss and a family history of bowel/ovarian cancer [14]. None of the patients had abdominal mass [14]. Conversely, high compliance was observed for the withdrawal of non-steroidal inflammatory drugs (NSAIDs) and antibiotics before testing [14]. Overall, only 24 requests (11%) were fully compliant for all criteria of the IBD clinical pathway [14].
Patient/clinician considerations
Unlike other fecal markers such as elastase, calprotectin is much less stable (up to 3 days at room temperature) and, therefore, it is important that patient samples are sent to the laboratory within 72 hours of collection [16]. It is still the case that samples are received by the laboratory with no date or time of collection and these are consequently rejected for analysis. Considering that calprotectin is elevated in gastrointestinal infection, in order for the test to be of clinical use, it is imperative that this is excluded.
The age restriction imposed on calprotectin testing is important and is based on the fact that IBS is more common in younger adults, that the prevalence of IBS decreases with increasing age and that new onset of symptoms after 50 years is uncommon [11, 17]. By focusing on this age group a large number of patients who do not require diagnostic testing will be excluded and, therefore, they will not add to the delay that current IBD sufferers face in receiving a colonoscopy.
Patients >40 years of age should be referred to Gastroenterology without delay, as the risk of developing colorectal cancer increases with age: colorectal cancer is the third most commonly diagnosed cancer in the UK and one of the major complications of IBD [18].
Since IBD is a relapsing disease the clinician should be aware that screening results from some patients with IBD may be negative, particularly if the disease is in a period of remittance and, therefore, the presentation of the patient, not the test result, should be the ultimate deciding factor over whether to refer. Finally, underpinning this is the need for local laboratories to determine their own method-specific cut-off values using evidence-based medicine. As with all screening tests the aim should be to optimize the test’s ability to exclude disease (IBS) so that fewer patients without disease are referred.
References
1. Trbojevic Akmacic I, Ventham NT, Theodoratou E, Vuckovic F, Kennedy NA, Krištic J, Nimmo ER, Kalla R, Drummond H, et al. Inflammatory bowel disease associates with proinflammatory potenial of the immunoglobulin G glycome. Inflamm Bowel Dis 2015; 21: 1237–1247.
2. de Souza HS, Fiocchi C. Immunopathogenesis of IBD: current state of the art. Nat Rev Gastroenterol Hepatol 2016; 186: 13–27.
3. Odze R. Diagnostic problems and advances in inflammatory bowel disease. Mod Pathol 2003; 16(4): 347–358.
4. Magro F, Giochetti P, Eliakim R, Ardissone S, Armuzzi A, Barreiro-de Acosta M, Burisch J, Gecse KB, Hart AL, et al. Third European evidence-based consensus on diagnosis and management of ulcerative colitis. Part1: definitions, diagnosis, extra-intestinal manifestations, pregnancy, cancer surveillance, surgery and ileo-anal pouch disorders. J Crohns Colitis 2017; 11(6): 649–670.
5. Salim SY, Söderholm JD. Importance of disrupted intestinal barrier in inflammatory diseases. Inflamm Bowel Dis 2011; 17(1): 362–381.
6. Ni J, Wu GD, Alenberg L, Tomov VT. Gut microbiota and IBD: causation or correlation? Nat Rev Gastroenterol Hepatol 2017; 14(10): 573–584.
7. Neurath MF. Cytokines in inflammatory bowel disease. Nat Rev Immunol 2014; 14(5): 329–342.
8. Műzes G, Molnár B, Tulassay Z, Sipos F. Changes of the cytokine profile in inflammatory bowel diseases. World J Gastroenterol 2012; 18(41): 5848–5861.
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The authors
Benjamin Palmer*1 PhD, MRSC; Wisam Jafar2 MBChB, MRCP(gastro), MSc, MA, FRCP; Steven McCann2 MSc, FRCPath
1Betsi Cadwaladr Health Board, Glan Clwyd Hospital, Rhyl, Denbighshire, Wales, UK
2Stockport NHS Foundation Trust, Stockport, Cheshire, UK
*Corresponding author
E-mail: Ben.palmer@wales.nhs.uk
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