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Unrestricted faecal calprotectin testing performs poorly in the diagnosis of inflammatory bowel disease in patients in primary care
  1. Samantha Conroy1,
  2. Melissa F Hale1,
  3. Simon S Cross2,
  4. Kirsty Swallow3,
  5. Reena H Sidhu1,
  6. Ravishankar Sargur3,
  7. Alan J Lobo1
  1. 1Department of Gastroenterology, Royal Hallamshire Hospital, Sheffield, UK
  2. 2Academic Unit of Pathology, University of Sheffield, Sheffield, UK
  3. 3Department of Immunology, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
  1. Correspondence to Profosser Alan J Lobo, Gastroenterology Unit, P Floor Royal Hallamshire Hospital, Sheffield S10 2JF, UK; alan.lobo{at}sth.nhs.uk

Abstract

Background Faecal 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.

Aims To assess the yield of IBD from FC testing in primary care.

Methods Retrospective 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.

Results 410 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%.

Conclusions FC 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
  • inflammatory bowel disease
  • colonoscopy
  • primary healthcare

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Footnotes

  • Handling editor Tahir S Pillay.

  • Contributors SC, MFH, KS, RHS, RS and AJL conceived and designed the study. SC undertook the data extraction. SC and SSC undertook data and statistical analysis. SC and AJL prepared the draft manuscript. All authors reviewed the manuscript, contributed to its drafting and approved the final version.

  • Competing interests AJL has received fees for lectures or as a member of advisory boards for Vifor Pharma, Takeda UK, Abbvie, Shield Therapeutics, Janssen and Dr Falk. Other authors have no competing interest to declare.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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