Abstract

Faecal calprotectin (FC) is a neutrophil-derived protein released in stool in response to mucosal inflammation. It is a simple, cheap and non-invasive test with high sensitivity and moderate specificity, which can be useful in the diagnosis and monitoring of inflammatory bowel disease (IBD). FC levels correlate well with bowel inflammation (both macroscopic and histological activity) and are not influenced by disease location or type of IBD. Despite the shortcoming with regards to specificity, it is the high sensitivity of FC that makes it a valuable screening tool in the diagnosis of IBD. It is especially effective in identifying children with low probability of IBD who would not benefit from further investigations. The cut-off value selected has a significant impact on the diagnostic accuracy of the test, influencing its sensitivity and specificity, and must be interpreted judiciously. Its role in disease monitoring is as an add-on test to Paediatric Ulcerative Colitis Activity Index and Paediatric Crohn's Disease Activity Index scores and can be used to differentiate disease relapse from functional symptoms. High levels of FC are also seen in a number of other conditions, such as gastrointestinal infections and coeliac disease. It is recommended that infective causes affecting the gut must be excluded first, before FC is measured.