Comparison of two immunoassays for measurement of faecal calprotectin in detection of inflammatory bowel disease: (pre)-analytical and diagnostic performance characteristics

The Reliability of Patient-Performed Fecal Calprotectin Testing in Inflammatory Bowel Disease

BACKGROUND

Home use of a buffer-containing extraction device for fecal calprotectin determination can bypass the labor-intensive extraction procedure and potentially prevent degradation at room temperature.

METHODS

In this prospective cross-sectional observational study, 2 CALiaGold tubes (extraction device) and one native tube were filled from the same bowel movement by patients with inflammatory bowel disease. Afterwards patients completed a questionnaire including whether they preferred the extraction device or the normal sampling method. All tubes were sent to the laboratory and when they arrived, 2 more CALiaGold tubes were filled at the laboratory from the native sample. The fecal calprotectin concentrations in all tubes were measured by a particle-enhanced turbidimetric immunoassay.

RESULTS

Fifty-three patients were included in the study. Fecal calprotectin levels were significantly higher in samples extracted by the patient compared to the analyst-performed extractions. When patients were divided into 3 groups (i.e., fecal calprotectin levels <50 ug/g, 50 to 200 µg/g, and >200 µg/g) a substantial concordance was found (Cohen kappa 0.654). Patients sampling imprecision was higher (P < 0.018, median CV 16%) compared to the analyst. Most patients preferred this extraction device.

CONCLUSIONS

Patient-performed fecal calprotectin extraction seems a realistic alternative sampling method and is preferred by most patients.

New Faecal Calprotectin Assay by IDS: Validation and Comparison to DiaSorin Method

Background: The faecal calprotectin (FC) measurement is used for inflammatory bowel disease (IBD) diagnosis and follow-up. The aim of this study was to validate for the first time the new IDS FC extraction device and immunoassay kit, and to compare it with the DiaSorin test in patients with and without IBD. Methods: First, the precision of the IDS assay and its stability were assessed. Then, 379 stool extracts were analysed with the IDS kit on iSYS and compared with a DiaSorin Liaison XL assay. Results: The intra- and inter-assay CVs did not exceed 5%. The stool samples were stable up to 4 weeks at −20 °C. Lot-to-lot comparison showed a good correlation (Lot1 = 1.06 × Lot2 + 0.60; p > 0.05). The Passing and Bablok regression showed no significant deviation from linearity between the two methods (IDS = 1.06 × DiaSorin − 0.6; p > 0.05; concordance correlation coefficient = 0.93). According to the recommended cut-offs, the IDS assay identified more IBD and irritable bowel syndrome patients than DiaSorin, which had more borderline results (16 vs. 20%, respectively). Conclusions: The IDS faecal calprotectin had good analytical validation parameters. Compared to the DiaSorin method, it showed comparable results, but slightly outperformed it in the identification of more IBD patients and active disease.

Impact of Preanalytical Factors on Calprotectin Concentration in Stool: A Multiassay Comparison

Background

Measuring calprotectin concentration in stool is increasingly important in monitoring disease activity and treatment response in inflammatory bowel disease. This study evaluates the impact of preanalytical storage conditions on reliability of calprotectin testing using 5 different calprotectin immunoassays.

Methods

Aliquots of homogenized fresh fecal samples in untreated or extracted form were stored at room temperature or 4°C. Calprotectin concentration was measured day 0 to 4 and 8. Five different immunoassays and accompanying extraction buffers were used (CALiaGold, Phadia EliA, Bühlmann fCal turbo, ELISA Bühlmann, Inova Quanta Flash). Repeated measurements of change from baseline calprotectin levels over time were analyzed using a mixed model analysis.

Results

Calprotectin concentrations declined over time under all preanalytical conditions with all assays, except for extracted feces stored at 4°C. The rate of decline was greatest in untreated stool kept at room temperature, reaching significant difference from baseline already after 1 day (P &lt; 0.001). In extracted feces kept at room temperature, significant difference from baseline was reached after 2 days, and in untreated feces at 4°C, after 4 days. However, the results differed significantly between assays. After 4 days of storage at room temperature, the mean calprotectin decline from baseline differed between 30% and 60%, dependent on the assay used.

Conclusions

Fecal calprotectin concentration in stool samples declines over time, and the rate of decline is greater at higher temperatures. In extracted feces stored at 4°C, calprotectin is most stable. It is assay-dependent how long extracted feces stored at 4°C give reliable test results.

Comparing outcomes from tailored meta-analysis with outcomes from a setting specific test accuracy study using routine data of faecal calprotectin testing for inflammatory bowel disease

Background

Meta-analyses of test accuracy studies may provide estimates that are highly improbable in clinical practice. Tailored meta-analysis produces plausible estimates for the accuracy of a test within a specific setting by tailoring the selection of included studies compatible with a specific setting using information from the target setting. The aim of this study was to validate the tailored meta-analysis approach by comparing outcomes from tailored meta-analysis with outcomes from a setting specific test accuracy study.

Methods

A retrospective cohort study of primary care electronic health records provided setting-specific data on the test positive rate and disease prevalence. This was used to tailor the study selection from a review of faecal calprotectin testing for inflammatory bowel disease for meta-analysis using the binomial method and the Mahalanobis distance method. Tailored estimates were compared to estimates from a study of test accuracy in primary care using the same routine dataset.

Results

Tailoring resulted in the inclusion of 3/14 (binomial method) and 9/14 (Mahalanobis distance method) studies in meta-analysis. Sensitivity and specificity from tailored meta-analysis using the binomial method were 0.87 (95% CI 0.77 to 0.94) and 0.65 (95% CI 0.60 to 0.69) and 0.98 (95% CI 0.83 to 0.999) and 0.68 (95% CI 0.65 to 0.71), respectively using the Mahalanobis distance method. The corresponding estimates for the conventional meta-analysis were 0.94 (95% CI 0.90 to 0.97) and 0.67 (95% CI 0.57 to 0.76) and for the FC test accuracy study of primary care data 0.93 (95%CI 0.89 to 0.96) and 0.61 (95% CI 0.6 to 0.63) to detect IBD at a threshold of 50 μg/g. Although the binomial method produced a plausible estimate, the tailored estimates of sensitivity and specificity were not closer to the primary study estimates than the estimates from conventional meta-analysis including all 14 studies.

Conclusions

Tailored meta-analysis does not always produce estimates of sensitivity and specificity that lie closer to the estimates derived from a primary study in the setting in question. Potentially, tailored meta-analysis may be improved using a constrained model approach and this requires further investigation.

The Toronto IBD Global Endoscopic Reporting [TIGER] Score: A Single, Easy to Use Endoscopic Score for Both Crohn's Disease and Ulcerative Colitis Patients

BACKGROUND AND AIMS

We constructed the Toronto IBD Global Endoscopic Reporting [TIGER] score for inflammatory bowel disease [IBD]. The aim of our study was to develop and validate the TIGER score against faecal calprotectin [FC], C-reactive protein [CRP], and IBD Disk.

METHODS

A cross-sectional study was performed among 113 adult patients (60 Crohn's disease [CD] and 53 ulcerative colitis [UC]). In the development and usability phase, blinded IBD experts reviewed and graded ileocolonoscopy videos. In the validity phase the TIGER score was compared with: [1] the Simple endoscopic Score for CD [SES-CD] and the Mayo endoscopic score in CD and UC, respectively; [2] FC and CRP; and [3] IBD Disk.

RESULTS

Inter-observer reliability of the TIGER score per segment between reviewers was excellent: interclass correlation coefficient [ICC] = 0.94 [95% CI: 0.92-0.96]. For CD patients, overall agreement per segment between SES-CD and TIGER was 91% [95% CI: 84-95] with kappa coefficient 0.77 [95% CI: 0.63-0.91]. There was a significant correlation between TIGER and CRP [p <0.0083], and TIGER and FC [p <0.0001]. In addition, there was significant correlation between TIGER and IBD Disk [p <0.0001]. For UC patients, overall agreement per segment between Mayo endoscopic score and TIGER was 84% [95% CI: 74%-90%] and kappa coefficient 0.60 [95% CI: 0.42-0.808]. There was a significant correlation between TIGER and FC [p <0.0001]. There was a significant correlation between TIGER and IBD Disk [p <0.0001].

CONCLUSIONS

The TIGER score is a reliable and simple novel endoscopic score that can be used for both CD and UC patients and captures full endoscopic disease burden.

Post-Induction High Adalimumab Drug Levels Predict Biological Remission at Week 24 in Patients With Crohn's Disease

INTRODUCTION

We investigated whether early adalimumab drug levels (ADL) at week 4 predicted biological remission at week 24.

METHODS

In a prospective study, we assessed clinical and biological remission at weeks 0, 4, 12, and 24 after induction of adalimumab in 33 patients with Crohn's disease. Disease activity was determined by the Harvey-Bradshaw Index, ileocolonoscopy reports, cross-sectional imaging, C-reactive protein (CRP), and fecal calprotectin (FC) levels. Clinical remission was defined as Harvey-Bradshaw Index <5. Biological remission was defined as a combination of FC < 200 μg/g and CRP <5 μg/mL. ADL trough levels were tested using a liquid phase, mobility shift assay.

RESULTS

At 24 weeks, 18/33 (55%) of the patients were with biological remission. Ten (30%) patients required dose escalation or withdrawal from adalimumab by week 24 because of lack of response and exhibited significantly higher FC (P = 0.003) and CRP (P = 0.002). ADL levels at week 4 (19.8 μg/mL vs 10.2 μg/mL, P = 0.001) were significantly higher in patients with biological remission vs nonresponders at week 24. ADL levels at week 4 were a good predictor of biological remission at week 24, with area under the curve 0.86, 95% confidence interval (1.1; 1.67) and for combined biological and clinical remission, with area under the curve 0.8. The best ADL cutoff at week 4 that predicted biological remission at week 24 was 13.9 μg/mL (sensitivity 94.4% and specificity 73.3%).

DISCUSSION

In individuals with Crohn's disease, higher adalimumab drug levels at week 4 (>13.9 μg/mL) were significantly associated with biological remission at week 24.

Test accuracy of faecal calprotectin for inflammatory bowel disease in UK primary care: a retrospective cohort study of the IMRD-UK data

OBJECTIVE

To estimate the test accuracy of faecal calprotectin (FC) for inflammatory bowel disease (IBD) in the primary care setting using routine electronic health records.

DESIGN

Retrospective cohort test accuracy study.

SETTING

UK primary care.

PARTICIPANTS

5970 patients (≥18 years) without a previous IBD diagnosis and with a first FC test between 1 January 2006 and 31 December 2016. We excluded multiple tests and tests without numeric results in units of µg/g.

INTERVENTION

FC testing for the diagnosis of IBD. Disease status was confirmed by a recorded diagnostic code and/or a drug code of an IBD-specific medication at three time points after the FC test date.

MAIN OUTCOME MEASURES

Sensitivity, specificity, and positive and negative predictive values for the differential of IBD versus non-IBD and IBD versus irritable bowel syndrome (IBS) at the 50 and 100 µg/g thresholds.

RESULTS

5970 patients met the inclusion criteria and had at least 6 months of follow-up data after FC testing. 1897 had an IBS diagnosis, 208 had an IBD diagnosis, 31 had a colorectal cancer diagnosis, 80 had more than one diagnosis and 3754 had no subsequent diagnosis. Sensitivity, specificity, and positive and negative predictive values were 92.9% (88.6% to 95.6%), 61.5% (60.2% to 62.7%), 8.1% (7.1% to 9.2%) and 99.6% (99.3% to 99.7%), respectively, at the threshold of 50 µg/g. Raising the threshold to 100 µg/g missed less than 7% additional IBD cases. Longer follow-up had no effect on test accuracy. Overall, uncertainty was greater for specificity than sensitivity. General practitioners' (GPs') referral decisions did not follow the anticipated clinical pathways in national guidance.

CONCLUSIONS

GPs can be confident in excluding IBD on the basis of a negative FC test in a population with low pretest risk but should interpret a positive test with caution. The applicability of national guidance to general practice needs to be improved.

Faecal calprotectin in inflammatory bowel diseases: a review focused on meta-analyses and routine usage limitations

A growing body of evidence has been published about the usefulness of measuring calprotectin in faecal samples (FCAL) in inflammatory bowel disease (IBD) assessment, including diagnosis, monitoring of disease activity and relapse prediction. Several systematic reviews with meta-analyses compiling studies for each particular clinical setting have been carried out in recent years. Most of these were focused on the use of FCAL in IBD diagnosis and showed a relevant role for this marker in selecting patients with gastrointestinal symptoms who would not need a further examination by endoscopy. Although a lesser number of meta-analyses have been performed on the use of FCAL as a surrogate marker of disease activity, a close correlation between FCAL and endoscopic activity of IBD has been shown. With respect to the predictive capacity of FCAL for IBD relapse, a single meta-analysis published indicates that this role is more limited. Furthermore, FCAL thresholds vary considerably depending on the clinical setting and, what is more concerning, among different commercially available assays due to a lack of FCAL concentration interchangeability. Here, we summarise recent publications about the role and limitations of FCAL in IBD, with a special focus on meta-analyses, and give an overview of alternative faecal biomarkers.

Analytical and clinical performance of the fully-automated LIAISONXL calprotectin immunoassay from DiaSorin in IBD patients

Objectives

Distinction between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) based on clinical symptoms is often difficult. In this study we assessed the performance of the fully-automated calprotectin immunoassay from DiaSorin in IBD diagnosis and follow-up and compared it to the EliA calprotectin 2 immunoassay.

Design

and Methods: The calprotectin immunoassay from DiaSorin run on the LIAISONXL was analytically and clinically validated and compared to the EliA calprotectin 2 immunoassay from Thermo Fisher Scientific run on the ImmunoCAP250. Five patient groups were measured (n ​= ​303): IBD: ulcerative colitis (UC) and Crohn’s disease (CD); non-IBD: IBS, other gastrointestinal diseases and controls (healthy patients with no gastrointestinal disease).

Results

The calprotectin immunoassay of DiaSorin showed good analytical performance with frozen samples. The presence of blood in the stool can interfere with the measurement of calprotectin. Patients suffering from IBD (UC or CD) showed significant higher concentrations of fecal calprotectin compared to controls (UC:710 ​± ​921 ​mg/kg; CD:967 ​± ​1243 ​mg/kg; controls:11±8 ​mg/kg) using DiaSorin’s immunoassay. The remaining non-IBD groups showed no significant difference compared to controls. Follow-up patients (n ​= ​9) showed a significant decrease in fecal calprotectin after treatment. At 50 ​mg/kg cut-off value, the negative predictive value for DiaSorin’s immunoassay was 96% and the positive predictive value 83% (sensitivity of 95% and specificity of 86%).

Conclusions

The lack of standardization contributes to the numerical differences between the two methods, but the qualitative conclusions do not differ. DiaSorin’s calprotectin immunoassay can be used both to distinguish between IBD and non-IBD patients as well as for follow-up of IBD patients.

•

New calprotectin immunoassay has a short sample preparation time and is easy to use.

•

DiaSorin’s immunoassay can be used to distinguish between high and low risk IBD patients, as opposed to IBS.

•

Differences observed between immunoassays are due to lack of standardization.

•

Blood in the stool can effect the calprotectin measurement.

Head to head comparison of two commercial fecal calprotectin kits as predictor of Mayo endoscopic sub-score and mucosal TNF expression in ulcerative colitis

BACKGROUND

Fecal calprotectin is widely used to monitor disease activity in patients with inflammatory bowel disease. Multiple commercial kits exist, however, since the analyses are not standardized, these kits cannot be used interchangeably. We aimed to perform a technical evaluation of two kits (Calpro from Calprolab, Norway and Calprest from Eurospital, Italy) and perform a tuning for detection of clinically relevant disease states in ulcerative colitis.

MATERIALS AND METHODS

For tuning against different clinical states a total of 116 patients with ulcerative colitis were recruited (67 of which were part of an earlier publication). For the technical evaluation an additional series of 80 random samples from the hospital lab were included. Technical evaluation was done by correlation and limits of agreement analysis; cut-off levels were explored by ROC analysis against clinically relevant actual states.

RESULTS

The technical evaluation revealed good correlation between assays, however a non-linear difference was found: At values below 200 mg/kg, no significant bias was found; in the interval 200-1000 mg/kg the Calprest assay measured on average 30% lower than Calpro; and at higher values Calprest measured 60% higher values than Calpro. Both assays predicted Mayo endoscopic score (MES) 0 (cutoff 28: sensitivity 0.38; specificity 0.82 for Calprest; cutoff 28: sensitivity 0.50; specificity 0.77 for Calpro), and MES 2-3 (cutoff 148: sensitivity 0.72; specificity 0.80 for Calprest; cutoff 208: sensitivity 0.64; specificity 0.80 for Calpro), but did not predict normalization of mucosal TNF transcript per se. A combination of calprotectin and MES predicted mucosal TNF transcript values reasonably well (Calpro: sensitivity 0.85, specificity 0.58; Calprest: sensitivity 0.85, specificity 0.61).

CONCLUSION

The Calpro and Calprest assays correlated well, but subtle differences were found, underlining the need for kit-specific cut-off values. Both kits were most precise in predicting active inflammation (MES 2-3), but less so for prediction of mucosal healing (MES 0) and normalization of mucosal TNF gene expression.

Faecal calprotectin as a diagnostic marker of inflammatory bowel disease in patients with gastrointestinal symptoms: meta-analysis

Colonoscopy is the standard medical procedure to identify inflammatory bowel disease (IBD) in patients with gastrointestinal symptoms. Noninvasive measurement of faecal calprotectin concentration may replace colonoscopy in this indication. The study aimed to assess efficacy of faecal calprotectin as a diagnostic marker of IBD in patients with symptoms suggestive of such diagnosis. Meta-analysis of diagnostic accuracy studies was performed. Cochrane, EMBASE and MEDLINE databases were searched until December 2018. Inclusion criteria comprised experimental and observational studies, adults with gastrointestinal symptoms, calprotectin as index and colonoscopy as reference test, presence of data on/enabling the calculation of diagnostic accuracy parameters. For each study, sensitivity and specificity of faecal calprotectin were analysed as bivariate data. Nineteen studies were identified. The total number of patients was 5032. Calculated pooled sensitivity and specificity were 0.882 [95% confidence interval (CI), 0.827-0.921] and 0.799 (95% CI, 0.693-0.875), respectively. Following faecal calprotectin incorporation in the diagnostic work-up of 100 people with suspected IBD, 18 non-IBD patients will have a colonoscopy performed and one patient with the disease will not be referred for this examination. Faecal calprotectin concentration measurement is a useful screening test to rule out IBD, at the same time reducing the need for colonoscopy by 66.7%.

The Clinical Accuracy of the BÜHLMANN fCAL ELISA in the Differentiation of Inflammatory Bowel Disease From Irritable Bowel Syndrome: A Multicenter Prospective Case–Control Study

Background

Fecal calprotectin (fCAL) is a noninvasive biomarker used to differentiate between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS).

Methods

A multicenter prospective case–control study evaluating the BÜHLMANN fCAL enzyme-linked immunosorbent assay (ELISA) was conducted in 478 subjects. Sensitivity, specificity, predictive values, and area under the receiver operator characteristic (AuROC) curve are reported and compared to another device.

Results

In differentiating IBD from IBS, the BÜHLMANN fCAL ELISA is very sensitive (93.3%) at a cutoff &lt;80 μg/g and balanced sensitivity (84.4%) and specificity (85.4%) at a cutoff &gt;160 μg/g (AuROC 0.933).

Conclusions

The BÜHLMANN fCAL ELISA demonstrates excellent discriminating between IBD and IBS.

Analytical Performance and Clinicopathologic Correlation of Four Fecal Calprotectin Methods

OBJECTIVES

Calprotectin is a noninvasive biomarker that can distinguish inflammatory bowel disease from irritable bowel syndrome. We investigated four automated fecal calprotectin methods on five different platforms for their preanalytical process, analytical performance, and clinicopathologic correlation.

METHODS

Four calprotectin methods (Bühlmann, EliA CN, EliA CN2, and DiaSorin) were performed on five platforms (Cobas 8000 E502, Phadia Immunocap 100 and 250, and Liaison and Liaison XL) in two hospital laboratories.

RESULTS

Overall variation for the different extraction devices was less than 19% when feces were of normal consistency. Freeze-thawing of samples resulted in comparable results compared with fresh samples. The different methods had a good analytic correlation (R = 0.83-0.95). Their clinicopathologic correlation was comparable, but the Bühlmann method showed significantly higher calprotectin values in every patient category.

CONCLUSIONS

The automated calprotectin methods showed a good performance and comparable clinicopathologic correlation. Due to lack of standardization, the numerical values differ for the various methods.

Faecal calprotectin determination: impact of preanalytical sample treatment and stool consistency on within- and between-method variability

Introduction

We assessed the differences in faecal calprotectin (FC) concentrations measured by two assays depending on the stool consistency and extraction method.

Materials and methods

Stool samples were extracted using the EliA Stool Extraction Kit, Calex® Cap extraction device and respective weighing methods, while FC concentrations were measured using the EliA^TM Calprotectin and Bühlmann fCAL® Turbo method and checked for within- and between-method variability with regard to extraction method and stool consistency category. Extraction yield was evaluated for impact of different sample incubation time (10 min and 1 h) in extraction buffer for both methods and for impact of different initial sample dilutions (1:50, 1:100, 1:500) for fCAL® Turbo method.

Results

Results determined from Calex® Cap extracts were higher compared to weighing method extracts (mean bias 33.3%; P < 0.001), while no significant difference was found between results obtained with EliA Stool Extraction Kit and weighing method (mean bias 0.1%; P = 0.484), in both cases irrespective of stool consistency. Bühlmann fCAL® Turbo results were higher than EliA^TM Calprotectin results (mean bias 32.3%, P = 0.025 weighing method; and mean bias 53.9%, P < 0.001 extraction devices), the difference is dependent on stool consistency and FC concentration. Significantly higher FC extraction yield was obtained with longer sample incubation time for both methods (P = 0.019 EliA^TM Calprotectin; P < 0.001 fCAL® Turbo) and with increasing initial sample dilution for fCAL® Turbo method (P < 0.001).

Conclusion

Preanalytical stool sample handling proved to be a crucial factor contributing to within- and between-FC assay variability. Standardization is urgently needed in order to assure comparable and reliable FC results.

Faecal calprotectin to detect inflammatory bowel disease: a systematic review and exploratory meta-analysis of test accuracy

OBJECTIVE

Test accuracy of faecal calprotectin (FC) testing in primary care is inconclusive. We aimed to assess the test accuracy of FC testing in primary care and compare it to secondary care estimates for the detection of inflammatory bowel disease (IBD).

METHODS

Systematic review and meta-analysis of test accuracy using a bivariate random effects model. We searched MEDLINE, EMBASE, Cochrane Library and Web of Science until 31 May 2017 and included studies from auto alerts up until 31 January 2018. Eligible studies measured FC levels in stool samples to detect IBD in adult patients with chronic (at least 6-8 weeks) abdominal symptoms in primary or secondary care. Risk of bias and applicability were assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 criteria. We followed the protocol registered as PROSPERO CRD 42012003287.

RESULTS

38 out of 2168 studies were eligible including five from primary care. Comparison of test accuracy by setting was precluded by extensive heterogeneity. Overall, summary estimates of sensitivity and specificity were not recorded. At a threshold of 50 µg/g, sensitivity from separate meta-analysis of four assay types ranged from 0.85 (95% CI 0.75 to 0.92) to 0.94 (95% CI 0.75 to 0.90) and specificity from 0.67 (95% CI 0.56 to 0.76) to 0.88 (95% CI 0.77 to 0.94). Across three different definitions of disease, sensitivity ranged from 0.80 (95% CI 0.76 to 0.84) to 0.97 (95% CI 0.91 to 0.99) and specificity from 0.67 (95% CI 0.58 to 0.75) to 0.76 (95% CI 0.66 to 0.84). Sensitivity appears to be lower in primary care and is further reduced at a revised threshold of 100 µg/g.

CONCLUSIONS

Conclusive estimates of sensitivity and specificity of FC testing in primary care for the detection of IBD are still missing. There is insufficient evidence in the published literature to support the decision to introduce FC testing in primary care. Studies evaluating FC testing in an appropriate primary care setting are needed.

Probiotics in cystic fibrosis patients: A double blind crossover placebo controlled study: Pilot study from the ESPGHAN Working Group on Pancreas/CF

BACKGROUND

A potential positive effect of probiotics in cystic fibrosis (CF) on fecal calprotectin (FCP), pulmonary exacerbations and weight has been described in small controlled trials.

METHODS

A double-blind multicenter cross-over study (2 × 4 m) was performed looking at abdominal pain, nutritional status, pulmonary function, pulmonary exacerbation, FCP and lactulose/mannitol gut permeability test. Patients kept a diary with daily scoring of abdominal pain, stool frequency and consistency as well as treatment changes.

RESULTS

31 CF patients entered the study of which 25 finished it. At start patients aged 9.3yrs (6.9-12.2), had a median BMI z-score of -0.5 (-1.5-0.08), height z-score of -0.4 (-1.1-0.05) and FEV1% of 100% (87.2-106.6). Median FCP at start was 61 μg/g (17-108) and gut permeability 0.079 (0.051-0.122). No significant changes were observed in the clinical parameters (BMI, FEV1%, abdominal pain, exacerbations). Despite being frequently abnormal (17/28 (61%) >50 mg/kg), FCP did not change significantly with probiotics. The proportion of patients with normal permeability was 8% during placebo and 32% during probiotic treatment (p = 0.031). FCP correlated to BMI z-score (p = 0.043) and gut permeability to abdominal pain (p = 0.015). The microbiome revealed a high predominance of Actinobacteria and Proteobacteriae. Probiotic supplementation did not result in a shift at the phylum nor at phylogenetic level.

CONCLUSION

Normalization of gut permeability was observed in 13% of patients during probiotic treatment. However, none of the previously described effects could be confirmed.

Fecal calprotectin correlates with active colonic inflammatory bowel disease but not with small intestinal Crohn's disease activity

Background

The utility of fecal calprotectin (FC) in small intestinal Crohn's disease (CD) is unclear. We examined how reliably FC reflects clinical and mucosal disease activity in small intestinal CD, colonic CD, and ulcerative colitis (UC).

Methods

A total of 72 Inflammatory Bowel Disease (IBD) patients (23 colonic CD, 14 isolated small intestinal CD, and 35 UC) were included. Clinical activity was assessed using the Harvey–Bradshaw Index (HBI) (CD) and Mayo score (UC). Inflammatory activity was assessed through ileocolonoscopy, cross‐sectional imaging, C‐reactive protein (CRP), and FC. Clinical activity was defined as HBI > 4 or Mayo clinical score ≥ 3. Endoscopy activity was defined as Mayo endoscopic subscore ≥ 1, SES‐CD score ≥ 3, and Rutgeerts > i1.

Results

In UC, FC was correlated with the Mayo clinical score (P < 0.0001) and was highly correlated with the total Mayo score (P < 0.0001). A cut‐off value of FC 100 μg/g provided sensitivity of 88% and specificity 100% for endoscopic activity. FC was lower for patients with endoscopic and clinical remission compared to active endoscopic disease (median 100 vs 1180 μg/g, P < 0.0001). In colonic CD, there was a significant correlation between FC and endoscopic activity (P < 0.001). For an FC cut‐off value of 100 μg/g, sensitivity was 100%, and specificity was 67%. In contrast, for isolated small intestinal CD, there was no significant correlation between FC and objective disease activity measured by either endoscopy or imaging (AUC 0.52, P = 0.58).

Conclusion

FC is reliable for the detection of colonic mucosal inflammation in both UC and CD but is less sensitive and reliable in the detection of small intestinal CD.

Predicting inflammatory bowel disease in children with abdominal pain and diarrhoea: calgranulin-C versus calprotectin stool tests

OBJECTIVE

Calgranulin-C (S100A12) is a new faecal marker of inflammation that is potentially more specific for inflammatory bowel disease (IBD) than calprotectin, since it is only released by activated granulocytes. We compared calgranulin-C and calprotectin to see which of the two tests best predicted IBD in children with chronic abdominal pain and diarrhoea.

DESIGN

Delayed-type cross-sectional diagnostic study.

SETTING AND PATIENTS

Previously undiagnosed patients aged 6-17 years, who were seen in paediatric clinics in the Netherlands and Belgium, sent in a stool sample for analysis. Patients with a high likelihood of IBD underwent upper and lower endoscopy (ie, preferred reference test), while those with a low likelihood were followed for 6 months for latent IBD to become visible (ie, alternative reference test). We used Bayesian modelling to correct for differential verification bias.

MAIN OUTCOME MEASURES

Primary outcome was the specificity for IBD using predefined test thresholds (calgranulin-C: 0.75 µg/g, calprotectin: 50 µg/g). Secondary outcome was the test accuracy with thresholds based on receiver operating characteristics (ROC) analysis.

RESULTS

IBD was diagnosed in 93 of 337 patients. Calgranulin-C had significantly better specificity than calprotectin when predefined thresholds were used (97% (95% credible interval (CI) 94% to 99%) vs 71% (95% CI 63% to 79%), respectively). When ROC-based thresholds were used (calgranulin-C: 0.75 µg/g, calprotectin: 400 µg/g), both tests performed equally well (specificity: 97% (95% CI 94% to 99%) vs 98% (95% CI 95% to 100%)).

CONCLUSIONS

Both calgranulin-C and calprotectin have excellent test characteristics to predict IBD and justify endoscopy.

TRIAL REGISTRATION NUMBER

NCT02197780.

Practical guidance on the use of faecal calprotectin

Differentiation between inflammatory bowel disease (IBD) and functional gut disorders, and the determination of mucosal disease activity in established cases of IBD remain the cornerstones of disease diagnosis and management. Non-invasive, accurate biomarkers of gut inflammation are needed due to the variability of symptoms, the inaccuracies of currently available blood markers and the cost and invasive nature of endoscopy. Numerous biomarkers have been used and/or considered with some in current use. This article reviews the current evidence base around the indications for using biomarkers and their limitations, with a particular focus on faecal calprotectin.

Elevation of serum pyruvate kinase M2 (PKM2) in IBD and its relationship to IBD indices

OBJECTIVES

Endoscopy remains the gold standard to diagnose and evaluate inflammatory bowel disease (IBD) activity. Current biomarkers or their combinations cannot adequately predict IBD risk, diagnosis, progression or relapse, and response to therapy. Pyruvate kinase M2 (PKM2) is emerging as a significant mediator of the inflammatory process. We aimed to assess levels of serum PKM2 in healthy and newly diagnosed IBD patients and its relationship with IBD indices and microbiota changes.

DESIGN AND METHODS

IBD serum samples from newly diagnosed patients were collected and analyzed using a PKM2-ELISA and correlated with disease activity scores, IBD disease type, and intestinal microbiota. Furthermore, we tested the genetic and protein expression of PKM2 in an in vitro intestinal cell model of inflammation.

RESULTS

Serum PKM2 levels were 6-fold higher in IBD patients compared to healthy controls, with no sensitivity to disease phenotype (Crohn's Disease or Ulcerative Colitis) or localization of inflammation. Serum PKM2 had considerably less interindividual variability than established IBD fecal biomarkers. A positive Pearson correlation (r=0.6121) existed between serum PKM2 and Bacteroidetes fecal levels in Crohn's disease (CD), while a negative (r=-0.6128) correlation was observed with Actinobacteria fecal levels. Furthermore, LPS (500ng/mL) significantly increased PKM2 expression in vitro, which was significantly suppressed by an anti-inflammatory flaxseed bioactive agent.

CONCLUSION

Our data suggests PKM2 as a putative biomarker for IBD and the dysbiosis of microflora in CD. Investigations involving larger number of clinical patients are necessary to validate its use as a serum biomarker of IBD.

Detection of calprotectin in inflammatory bowel disease: Fecal and serum levels and immunohistochemical localization

The aim of the present study was to quantify calprotectin levels using an enzyme-linked immunosorbent assay (ELISA) and a point-of-care test (POCT) in patients with inflammatory bowel disease. Overall, 113 patients with ulcerative colitis (UC; 51 men and 62 women) and 42 patients with Crohn's disease (CD; 29 men and 13 women), who were scheduled to undergo a colonoscopy, were prospectively enrolled and scored endoscopically and clinically. An additional 96 healthy, age-matched subjects served as the normal controls. Feces and blood samples from the patients with UC and CD, and the normal controls were analyzed. These patients had received adequate medical treatment. The tissue distribution of calprotectin was investigated using immunohistochemistry. The fecal calprotectin levels, as measured using an ELISA, were correlated with the endoscopic and clinical disease activities and laboratory parameters, including serum levels of hemoglobin (Hb), albumin and C-reactive protein, and erythrocyte sedimentation rate, particularly among the patients with UC. The fecal Hb level was close to that of the fecal calprotectin level (r=0.57; P<0.0001). The fecal calprotectin level measured using an ELISA was well-correlated with the fecal calprotectin level measured using the POCT (r=0.81; P<0.0001), but was not correlated with the serum calprotectin level (r=0.1013; P=0.47). An immunohistochemical investigation revealed that patients with both UC and CD had higher neutrophil and monocyte/macrophage calprotectin-positive cell expression levels, compared with those in the normal controls. Fecal calprotectin was considered a reliable marker for disease activity, and the assessment of fecal calprotectin via POCT showed potential as a rapid and simple measurement in clinical settings.

Analytical performance and diagnostic accuracy of six different faecal calprotectin assays in inflammatory bowel disease

BACKGROUND

We evaluated the analytical performance of six different faecal calprotectin immunoassays together with their diagnostic accuracy in the discrimination between functional and organic bowel disorders.

METHODS

The faecal samples were obtained from inflammatory bowel disease patients (n=27) at the time of diagnosis [Crohn's disease (n=15), colitis ulcerosa (n=12)], gastroenterologic disease control patients (n=52) and rheumatologic disease control patients (n=26). All individuals included in the study underwent a concurrent ileocolonoscopy. Analytical performance (imprecision, accuracy, carry-over, correlation and agreement) and diagnostic accuracy (sensitivity, specificity, likelihood ratios) of the different assays were evaluated.

RESULTS

All methods demonstrated good analytical performance, but within-run and total imprecision varied depending on the assay methodology used. Using Passing Bablok and Bland-Altman analyses, low quantitative agreement was observed between the assays. All assays showed excellent diagnostic accuracy, with areas under the receiver operating characteristic curves (ROC) ranging from 0.974 to 0.998. The AUCs were not significantly different between assays (p>0.05). Diagnostic sensitivity at the cut-off at a fixed specificity of 75% ranged from 95.2% to 100%. Introduction of multiple result intervals increased the clinical interpretation of all the assays.

CONCLUSIONS

Analytical and diagnostic performance of the evaluated faecal calprotectin assays is good, but numerical values differ substantially between the assays necessitating the use of different clinical cut-offs. Introduction of multiple result intervals aids in clinical decision-making.

Analytical and diagnostic performance of two automated fecal calprotectin immunoassays for detection of inflammatory bowel disease

BACKGROUND

We evaluated the (pre-)analytical and diagnostic performance of two automated fecal calprotectin (FC) immunoassays, Liaison® Calprotectin (Diasorin) on Liaison® XL and fCAL™ turbo (Bühlmann laboratories AG) on Cobas C501 (Roche Diagnostics), and compared it with our established Bühlmann ELISA method.

METHODS

Our study comprised 229 consecutive patients with clinical suspicion of inflammatory bowel disease (IBD).

RESULTS

All assay related stool extraction procedures showed excellent correlation with the established method, but the new stool extraction devices tend to give higher results as compared with stool weight methods. Both automated assays demonstrated good performance in terms of precision (CVt≤8.1%), accuracy (bias≤6.7%) and total error (≤16.4%). Method comparison with established enzyme linked immunosorbent assay (ELISA) showed good correlation (rs>0.925), but regression analysis showed significant proportional differences. Diagnostic performance characteristics with regard to diagnosis of IBD were good and in line with other reports. In addition, we were able to show that optimization of manufacturer's cut-off and moreover, the introduction of a gray zone resulted in a significant increase of post-test probability.

CONCLUSIONS

In conclusion, the newly developed stool extraction device protocols showed acceptable and comparable performance to the stool weight method. Overall, the automated Liaison® Calprotectin and fCAL™ turbo assay showed good analytical and diagnostic performance for detection of IBD.

Effect of faecal calprotectin assay variability on the management of inflammatory bowel disease and potential role of faecal S100A12

Aims

To prospectively evaluate whether between-assay variability of different faecal calprotectin (f-Cp) assays influences diagnostic accuracy for inflammatory bowel disease (IBD) in a cohort of patients with confirmed IBD and irritable bowel syndrome (IBS). To also evaluate the diagnostic accuracy of faecal S100A12 (f-S100A12) against f-Cp in the same patient cohort and assess whether f-S100A12 offers additional diagnostic value.

Methods

F-Cp using four commercially available f-Cp assays, f-S100A12 and blood biomarkers were measured in patients, recruited from the local IBD clinic, who had established IBS or active ulcerative colitis (UC) and Crohn’s disease (CD). Diagnostic sensitivities and specificities for each assay and biomarker were calculated and compared.

Results

Median f-Cp levels in all assays were significantly higher in UC (347–884 µg/g; n=28) and CD (377–838 µg/g; n=15) compared with IBS (6–27 µg/g; n=17). Sensitivities and specificities at 50 µg/g were 94%–100% and 82%–100%, respectively. Median f-S100A12 levels were significantly higher in UC (81.0 µg/g; IQR 38.3–159.8) and CD (47.2 µg/g; IQR 5.3–108.9) compared with IBS (0.7 µg/g; IQR 0.5–0.8). At 2.8 µg/g, f-S100A12 had a sensitivity of 97% and specificity of 94%. The blood biomarkers demonstrated sensitivities and specificities of 44%–63% and 80%–92%, respectively.

Conclusions

The diagnostic sensitivity of the calprotectin assays was similar despite inter-kit variability in absolute values. There is a need for f-Cp assay standardisation, but in its absence assay-specific cut-off values may optimise their diagnostic performance. F-S100A12 demonstrated comparable sensitivity and specificity to f-Cp and although a research tool at present, may have a future role to play in the diagnosis and management of these patients.

Clinical implications of assay specific differences in f-calprotectin when monitoring inflammatory bowel disease activity over time

OBJECTIVE

With several faecal calprotectin (FC) assays on the market, it has been difficult to define a uniform threshold for discriminating between remission and active disease in patients with inflammatory bowel disease (IBD). We aimed to compare the results of different FC-assays in IBD patients, followed over time.

MATERIAL AND METHODS

IBD patients provided faecal samples and reported clinical activity every third month prospectively over a two year period. FC was measured with two ELISA - (Bühlmann and Immunodiagnostik) and one automated fluoroimmunoassay (Phadia).

RESULTS

In total, 13 patients provided 91 faecal samples. The median (IQR) concentration of FC was higher at active disease than at remission for all assays: Bühlmann 845 (1061-226) μg/g versus 62 (224-39) μg/g, Phadia 369 (975-122) μg/g versus 11 (52-11) μg/g, and Immundiagnostik 135 (302-69) μg/g versus 8 (56-4) μg/g. The Bühlmann assay produced the largest absolute difference but the corresponding relative difference seemed to be more pronounced when analysed by the Phadia - (ratio of means 8.5; 95% CI 3.3-21.9) or the Immundiagnostik assay (ratio of means 7.4; 95% CI 3.1-17.6) than by the Bühlmann assay (ratio of means 5.3; 95% CI 2.7-10.6). Consequently, the specificity for discriminating active disease from remission varied between assays (34-75%) when the cut-off 50 μg/g was used, whereas the differences in sensitivity were less pronounced.

CONCLUSIONS

Cross-comparisons revealed overall poor agreement between the assays as well as differences in the dynamics of FC. These findings suggest that standardisation of the method is needed to implement FC as a disease monitoring tool at large-scale.

Comparison of Fecal Calprotectin Methods for Predicting Relapse of Pediatric Inflammatory Bowel Disease

Background. Pediatric inflammatory bowel disease (IBD) is on the rise worldwide. Endoscopies are necessary for IBD assessment but are invasive, expensive, and inconvenient. Recently, fecal calprotectin (FCal) was proposed as a noninvasive and specific marker of gut inflammation. We evaluated the analytical performance of three FCal assays and their clinical performance in predicting relapse in pediatric IBD. Methods. This study used 40 pediatric IBD and 40 random non-IBD patients' fecal samples. Two automated ELISAs (Bühlmann and PhiCal® Calprotectin-EIA) and an EliA (Phadia 250 EliA-Calprotectin) were used to evaluate the analytical performance. The clinical performance was assessed by PhiCal Calprotectin-EIA, EliA-Calprotectin, and Bühlmann immunochromatographic point-of-care test (POCT). Results. All assays displayed acceptable analytical performance below and above the medical decision cut-off [imprecision (CV < 10% intra-assay; <15% interassay); linearity (overall mean % deviation < 16.5%)]. The agreement with PhiCal Calprotectin-EIA was 100% and 78.6% for Bühlmann (95% CI, 87.5-100; Kappa: 1) and EliA-Calprotectin (95% CI, 60.5-89.8; Kappa: 0.32), respectively, and 63.6% between Bühlmann and EliA-Calprotectin (95% CI, 46.6-77.8; Kappa: 0.16). All assays evaluated had similar clinical performance [AUC: 0.84 (EliA-Calprotectin); 0.83 (POCT and PhiCal Calprotectin-EIA)]. Conclusion. FCal levels determined using the same method and assay together with clinical history would be a noninvasive and useful tool in monitoring pediatric IBD.

Usefulness of a rapid faecal calprotectin test to predict relapse in Crohn's disease patients on maintenance treatment with adalimumab

BACKGROUND AND AIM

Predicting relapse in Crohn's disease (CD) patients by measuring non-invasive biomarkers could allow for early changes of treatment. Data are scarce regarding the utility of monitoring calprotectin to predict relapse. The aim of the study was to evaluate the predictive value of a rapid test of faecal calprotectin (FC) to predict for flares in CD patients on maintenance treatment with adalimumab (ADA).

METHODS

A prospective, observational cohort study was designed. Inclusion criteria were CD patients in clinical remission on a standard dose of ADA therapy. Fresh FC was measured using a rapid test.

RESULTS

Thirty patients were included (median age 38 years, 56.7% female). After the 4 months follow-up, 70.0% patients remained in clinical remission and 30.0% had a relapse. FC concentration at inclusion was significantly higher in those patients who relapsed during the follow-up (625 μg/g) compared to those who stayed in remission (45 μg/g). The optimal cut-off for FC to predict relapse was 204 μg/g. The area under the receiver-operating characteristic curve was 0.968. Sensitivity, specificity, positive, and negative predictive value of FC to predict relapse were 100%, 85.7%, 74.1%, and 100%, respectively.

CONCLUSION

In CD patients on ADA maintenance therapy, FC levels measured with a rapid test allow relapse over the following months to be predicted with high accuracy. Low FC levels exclude relapse within at least 4 months after testing, whereas high levels are associated with relapse in three out of every four patients.

Accuracy of three different fecal calprotectin tests in the diagnosis of inflammatory bowel disease

Background/Aims

Several studies have found that the measurement of fecal calprotectin is useful for the early diagnosis of inflammatory bowel disease (IBD). We compared the effectiveness of three different fecal calprotectin kits for initial diagnosis in patients with suspected IBD.

Methods

We enrolled 31 patients with IBD (18 Crohn's disease [CD], 11 ulcerative colitis [UC], and two intestinal Behçet's disease), five with irritable bowel syndrome (IBS), and five with other colitis (four infectious colitis and one intestinal tuberculosis). Diagnosis was based on clinical, laboratory, and endoscopic examinations. Fecal samples were obtained at the first diagnosis and calprotectin levels were measured using three different kits (Quantum Blue® Calprotectin, EliA™ Calprotectin, and RIDASCREEN® Calprotectin).

Results

The overall accuracy for differentiating IBD from IBS or other colitis was 94% and 91%, respectively, for Quantum Blue® (cutoff, 50 µg/g); 92% and 89%, respectively, for EliA™ (cutoff, 50 µg/g); and 82% and 76%, respectively, for RIDASCREEN® (cutoff, 50 µg/g). In patients with CD, the results of Quantum Blue® Calprotectin and EliA™ Calprotectin correlated significantly with levels of the Crohn's disease activity index (Spearman's rank correlation coefficient, r=0.66 and r=0.49, respectively). In patients with UC, the results of EliA™ Calprotectin correlated significantly with the Mayo score (r=0.70).

Conclusions

Fecal calprotectin measurement is useful for the identification of IBD. The overall accuracies of the three fecal calprotectin kits are comparable.

Low Fecal Calprotectin Correlates with Histological Remission and Mucosal Healing in Ulcerative Colitis and Colonic Crohn's Disease

BACKGROUND

Data regarding the correlation of histologic and endoscopic healing with fecal calprotectin (FC) are conflicting. We examined how FC levels correlate with histological and endoscopic remission in colonic inflammatory bowel disease.

METHODS

Fifty-eight patients (23 with colonic Crohn's disease [CD] and 35 with ulcerative colitis [UC]) were included. Clinical activity was assessed by Harvey-Bradshaw index (CD) and Mayo score (UC). Inflammatory activity was assessed by ileocolonoscopy, C-reactive protein, and FC. Clinical remission was defined as Harvey-Bradshaw index ≤ 4 or Mayo score ≤ 2 and mucosal healing as Mayo endoscopic subscore = 0 (UC), and Simple Endoscopic Score-CD <3 (CD). Histologic activity was assessed in 27 patients (15 CD, 12 UC). Histological remission was defined as absence of active inflammation (Geboes score <3.1) and absence of basal plasmacytosis.

RESULTS

In UC, FC correlated with clinical Mayo score (r = 0.63, P < 0.0001). This correlation was strengthened by adding the endoscopic subscore (r = 0.90, P < 0.0001). The endoscopic subscore also independently correlated with FC (r = 0.96, P < 0.0001). In Crohn's colitis, endoscopic activity correlated with FC (r = 0.61, P < 0.001). FC levels were lower overall for patients with endoscopic remission compared with active endoscopic disease (median 100 versus 1180 μg/g, P < 0.0001). FC also correlated with histological remission (Geboes score < 3.1) and absence of basal plasmacytosis in CD (r = 0.77, r = 0.80, respectively; P < 0.01). Area under the curve for FC as a predictor of histological remission (Geboes score <3.1) was 0.95 (95% CI, 0.82-1).

CONCLUSIONS

Low FC correlates well with histological remission and mucosal healing in colonic inflammatory bowel disease and is thus a clinically useful surrogate for inflammatory activity.

Fecal Calprotectin as Predictor of Relapse in Patients With Inflammatory Bowel Disease Under Maintenance Infliximab Therapy

BACKGROUND AND GOALS

Predicting relapse in Inflammatory Bowel Disease (IBD) could allow for early changes of treatment. Close monitoring of fecal calprotectin (FC) could be useful to predict relapse in IBD. Aim of the study was to evaluate the predictive value of a rapid FC test to predict flares in patients with IBD under maintenance therapy with Infliximab.

STUDY

A prospective observational cohort study was designed. IBD patients in clinical remission under maintenance Infliximab therapy were included. FC was measured using a rapid test on a stool sample obtained within 24 hours before Infliximab infusion. Clinical examination was performed 2 months after that infusion.

RESULTS

Fifty-three patients were included (52.8% female). Thirty-three patients (62.3%) had Crohn's disease and 20 (37.7%) had ulcerative colitis. All patients were in remission at inclusion. After 2 months, 41 patients (77.4%) remained in clinical remission and 12 (22.6%) presented a relapse. FC (mean±SD) in relapsing and not-relapsing disease was 332±168 and 110±163 µg/g, respectively (P<0.005). A FC concentration>160 µg/g had a sensitivity of 91.7%, and specificity of 82.9% to predict relapse.

CONCLUSIONS

In IBD patients under Infliximab maintenance therapy, high FC levels allow predicting relapse within the following 2 months. Long-term remission is associated with low calprotectin levels. Further studies are required to confirm these results.

Fecal calprotectin for diagnosis of digestive system diseases

Calprotectin is a 36 kDa calcium- and zinc-binding protein that belongs to the S100 family. Calprotectin shows an excellent stability in feces and appears to be superior to conventional fecal markers. Fecal calprotectin concentrations closely correlate with the fecal excretion of in-labelled leukocytes. In addition, fecal calprotectin has an overall high specificity. Therefore, it could be a useful marker for diagnosis of intestinal diseases. In this review we summarize the structure, physical and chemical characteristics of fecal calprotectin and analyze the relationship between calprotectin and intestinal diseases.

Validation of a new extraction device for measuring faecal calprotectin in inflammatory bowel disease, and comparison to established extraction methods

OBJECTIVE

Faecal (f-) calprotectin is a widely used surrogate marker of intestinal inflammation. F-calprotectin analysis is labour demanding partly due to a time consuming extraction step. The aim of this project was to validate a new extraction method for f-calprotectin.

MATERIAL AND METHODS

A prospective multicentre study included 135 patients with an established diagnosis of inflammatory bowel disease. The patients submitted a faeces sample, which was extracted with both the conventional method at the participating laboratory and the new extraction device. The extracts were analyzed by an automated ELISA instrument.

RESULTS

Method comparison of the traditional method and the new device showed a slope of 1.01 (0.93-1.07) with intercept of - 2.2 (- 4.9-0.6). The Spearman rank correlation coefficient was 0.96.

CONCLUSIONS

The new extraction device is a reliable and time saving alternative to the conventional extraction method.

Faecal leukocyte esterase activity is an alternative biomarker in inflammatory bowel disease

Leukocyte cytosolic proteins (e.g., calprotectin) are emerging biomarkers for inflammatory bowel disease. Leukocyte aryl esterase activity has been commonly used for sensitive detection of leukocytes in human body fluids such as urine. Urine test strip results are generally reported in categories. As automated strip readers allow quantitative data to be reported, sensitive quantitative detection of leukocytes in body fluids has become possible. Here, we explored the use of leukocyte esterase as a potential alternative faecal biomarker for inflammatory bowel disease.

We evaluated leukocyte esterase activity in faecal extracts and compared Cobas u 411 (Roche) quantitative reflectance data with calprotectin concentration for 107 routine samples. Stability of leukocyte esterase for trypsin digestion was carried out by adding trypsin to the extract. Incubation occurred at 37 °C for 24 h or 48 h.

Reproducibility of the reflectance signal was good (within-run imprecision: 6.1%; between-run imprecision: 6.2%). Results were linear in the range 10

Quantitative leukocyte esterase activity of faecal extracts provides information about the leukocyte count in the gut lumen. Leukocyte esterase is a promising and affordable alternative biomarker for monitoring inflammatory bowel disease.

Proteolysis is a confounding factor in the interpretation of faecal calprotectin

Calprotectin is a 36 kDa calcium and zinc binding protein. An increased level of calprotectin points towards inflammatory bowel disease. However, the biomarker calprotectin shows 14 potential cleavages sites for trypsin. Next to trypsin, also the presence of its inhibitor α

An in vitro model was created. As calprotectin source, leukocytes were isolated and subsequently lysed (1% Triton X-100) and diluted in faecal matrix. Trypsin digestion was carried out by adding trypsin. Incubation occurred for 24 h or 48 h (37 °C). To study the influence of α

In vitro experiments enabled monitoring of the faecal calprotectin digestion, leading to loss of immunoreactivity. Trypsin activity was a potential confounder in the interpretation of calprotectin, in particular for proximal lesions, where exposure of calprotectin to trypsin is prolonged. Relative calprotectin loss was proportional to the amount of trypsin. Decrease of calprotectin was more pronounced after 48 h of incubation in comparison to 24 h of incubation. Analogue experiments also showed stable calprotectin values after adding α

Transit time, trypsin activity and addition of blood as a source of α