Unrestricted faecal calprotectin testing performs poorly in the diagnosis of inflammatory bowel disease in patients in primary care

Abstract

BackgroundFaecal calprotectin (FC) measurement distinguishes patients with inflammatory bowel disease (IBD) from those with irritable bowel syndrome but evidence of its performance in primary care is limited.AimsTo assess the yield of IBD from FC testing in primary care.MethodsRetrospective review of hospital records to assess the outcome following FC testing in primary care. Investigations for all patients undergoing FC testing in a single laboratory for 6 months from 1 October 2013 to 28 February 2014 were reviewed.Results410 patients (162 male; median age 42; range 16–91) were included. FC>50 µg/g was considered positive (FC+). 148/410 (36.1%; median age 44 (17–91)) were FC+ (median FC 116.5 µg/g (51–1770)). 122/148 FC-positive patients (82.4%) underwent further investigation. 97 (65.5%) underwent lower gastrointestinal endoscopy (LGIE), of which 7 (7.2%) had IBD. 49/262 (18.7%) FC-negative (FC−) patients (FC ≤50 µg/g) (median age 47 (19–76)) also underwent LGIE, of whom 3 (6.1%) had IBD.IBD was diagnosed in 11/410 (2.7%; 4 ulcerative colitis, 3 Crohn’s disease, 4 microscopic colitis). 8/11 were FC+ (range 67–1170) and 3 FC−. At a 50 µg/g threshold, sensitivity for detecting IBD was 72.7%, specificity 64.9%, positive predictive value (PPV) 5.41% and negative predictive value 98.9%. Increasing the threshold to 100 µg/g reduced the sensitivity of the test for detecting IBD to 54.6%.ConclusionsFC testing in primary care has low sensitivity and specificity with poor PPV for diagnosing IBD. Its use needs to be directed to those with a higher pretest probability of disease. Local services and laboratories should advise general practitioners accordingly.

Faecal calprotectin effectively excludes inflammatory bowel disease in 789 symptomatic young adults with/without alarm symptoms: a prospective UK primary care cohort study

“…This is not only due to the low prevalence of colorectal cancer in this age group, but also the clinical acumen of primary care physicians, meaning that calprotectin can safely be applied in young patients with gastrointestinal alarm symptoms deemed unsuitable for urgent referral using current national cancer guidelines by their GP (NICE, NG12). 8 Existing studies of the performance of calprotectin for distinguishing organic from nonorganic intestinal diseases, that mostly excluded patients with gastrointestinal alarm symptoms, report negative predictive values of 98 to 99%, and positive predictive values 14 to 40%; the wide variation in the latter reflecting the impact that age and presenting symptoms have on the prevalence of disease …”

“…In the light of our findings, we will continue to allow GPs to use the test in patients with gastrointestinal alarm symptoms and will make the following revisions to our calprotectin pathway: a single 100 μg/g calprotectin cut‐off; eight‐week safety‐net review of nonreferred calprotectin negative patients; closer oversight by a lead clinician; and sending patients with a calprotectin ≥250 μg/g straight‐to‐test, as over two‐thirds (68% [30/44]) will have IBD once infective conditions have been excluded. Indeed, the presence of alarm symptoms, which raise the pre‐test probability of IBD, may be crucial to the successful application of calprotectin diagnostic pathways in primary care; without which the PPV of calprotectin may too low to be clinically useful in identifying IBD . Further research is required to establish how calprotectin will integrate with faecal immunochemical testing (FIT), in particular in older age‐groups than included here …”

“…Indeed, the presence of alarm symptoms, which raise the pre-test probability of IBD, may be crucial to the successful application of calprotectin diagnostic pathways in primary care; without which the PPV of calprotectin may too low to be clinically useful in identifying IBD. 21 Further research is required to establish how calprotectin will integrate with faecal immunochemical testing (FIT), in particular in older age-groups than included here. 20,[23][24][25] Our service evaluation demonstrates that faecal calprotectin is a clinically useful primary care test to distinguish IBD and organic intestinal disease as a whole from functional gut disorder in patients aged less than 46.…”

A validated risk stratification tool for detecting high‐risk small bowel Crohn's disease

“…Faecal calprotectin, for example, while a widely available and objective test, is expensive in Australia and North America, and not currently covered by government rebated health care in most settings. Recent studies have questioned its performance for the diagnosis of IBD in the community setting, and especially for small bowel CD phenotypes …”

“…Recent studies have questioned its performance for the diagnosis of IBD in the community setting, and especially for small bowel CD phenotypes. [25][26][27] This situation results in access limitations in community and regional practices-the target population for our tool. In addition, a subgroup of individuals in the community struggle to accept a pathology test based on self-collection of a faecal specimen.…”