Elevated Faecal Calprotectin Levels are a Reliable Non-Invasive Screening Tool for Small Bowel Crohn’s Disease in Patients Undergoing Capsule Endoscopy

Background: Approximately 10% of Crohn’s disease (CD) patients have this disease affecting the small bowel (SB) beyond the reach of Ileo-colonoscopy. Capsule endoscopy (SBCE) is the recommended investigation for SB disease. An accurate and inexpensive biomarker would help identify at-risk patients. Aim: To examine the efficacy of faecal calprotectin (FC) and C-reactive protein (CRP) as predictors of SBCE findings in suspected and known CD. Methods: A prospective observational study. Consecutive patients referred for SBCE gave FC and CRP samples. The diagnostic accuracy for SB CD based on SBCE result was calculated for both FC and CRP. Results: Of 100 invitees, FC and SBCE results were available in 64 cases. Correlation between FC >50 µg/g and SBCE result was poor К = 0.163; sensitivity, specificity, positive predictive value (PPV) and negative predictive values for ileitis were 60, 61, 32 and 83% respectively. PPV and specificity improved at FC >100 µg/g, 76 and 40%, correlation remained fair, К = 0.259. Receiver operating characteristic analysis had a sensitivity of 47% and specificity of 90% for FC >194 µg/g. CRP alone or in combination was an inaccurate predictor of ileitis. Conclusion: Our study suggests that FC level >194 µg/g may be a useful SBCE filter test, identifying patients at risk of SB CD.