Calprotectin

Calprotectin is a protein found in neutrophils. If there is increased infection or inflammation in the gut, calprotectin can be found at increased levels in the faeces. It is a particularly useful test when differentiating between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). The test has a reported sensitivity of 95% and specificity of 91% at a cut-off of 50 microg/g when differentiating patients with IBD from healthy controls.

Faecal calprotectin (FCAL) is used to assist in the differentiation between IBD and IBS, and should be measured if a diagnosis of IBD or a secondary care referral for IBD is being considered. In patients with clear indications of IBS, measurement of FCAL is not necessary.

Testing of FCAL may be appropriate in patients under the age of 50 with the following symptoms:

• Cramping lower abdominal pain and/or pre-defecatory pain
• Lower abdominal bloating
• Changes in bowel habit e.g. looser or harder stools, increased or decreased frequency
• Passing blood or mucus PR
• Bloody diarrhoea

FCAL is also used to monitor disease activity in patients with known IBD.

• If cancer is suspected
• Patients >50 years of age

Non-steroidal anti-inflammatory drugs (NSAIDs) and proton-pump inhibitors (PPI) can cause false elevations in FCAL due to short term inflammatory gut responses. FCAL is also elevated during viral and bacterial gastroenteritis; therefore FCAL testing during and immediately after episodes of gastroenteritis may produce misleading results.

For patients with borderline raised/equivocal results repeat testing may be recommended by some healthboards after a set period of time. If patients are on NSAIDs or PPIs, it may be advisable to repeat the test in 8-12 weeks if an equivocal result is received; alternatively, medications may be temporarily discontinued under clinical guidance.

1. Kennedy NA, Clark A, Walkden A, Chang JC, Fascí-Spurio F, Muscat M, et al. Clinical utility and diagnostic accuracy of faecal calprotectin for IBD at first presentation to gastroenterology services in adults aged 16-50 years. J Crohns Colitis. 2015 Jan;9(1):41-9. Available from: https://academic.oup.com/ecco-jcc/article/9/1/41/485625 doi: 10.1016/j.crohns.2014.07.005
2. NICE DG11 - Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel. Published 2013, reviewed in 2017 Available from: https://www.nice.org.uk/guidance/dg11
3. Tibble JA, Sigthorsson G, Foster R, Scott D, Fagerhol MK, Roseth A, Bjarnason I. High prevalence of NSAID enteropathy as shown by a simple faecal test. Gut. 1999 Sep;45(3):362-6. Available from: https://gut.bmj.com/content/45/3/362 doi: 10.1136/gut.45.3.362
4. Poullis A, Foster R, Mendall MA, Shreeve D, Wiener K. Proton pump inhibitors are associated with elevation of faecal calprotectin and may affect specificity. Eur J Gastroenterol Hepatol. 2003 May;15(5):573-4; author reply 574. Available from: https://journals.lww.com/eurojgh/Citation/2003/05000/Proton_pump_inhibitors_are_associated_with.21.aspx doi: 10.1097/00042737-200305000-00021
5. Jukic A, Bakiri L, Wagner EF, Tilg H, Adolph TE. Calprotectin: from biomarker to biological function. Gut. 2021 Oct;70(10):1978-1988. Available from: https://gut.bmj.com/content/70/10/1978.long doi: 10.1136/gutjnl-2021-324855
6. NHS Lothian RefHelp - Faecal calprotectin. Available here