Background and aim: Fecal calprotectin (FC) is a non-invasive marker of gastrointestinal inflammation with advocated diagnostic precision in distinguishing inflammatory bowel disease (IBD) from non-IBD diagnoses. FC correlates with abnormalities seen on small bowel barium radiology, but little data exist in relation with small bowel capsule endoscopy (SBCE). To investigate the value of FC as a selection tool for further investigation of the small bowel with SBCE, in a cohort of patients who had negative bi-directional endoscopies, but with continuing clinical suspicion of Crohn's disease (CD).
Methods: We retrospectively correlated the findings of SBCE with FC levels in patients referred with clinical suspicion of CD and negative bi-directional endoscopies. Only patients with FC results prior to the SBCE test were included; in cases of multiple FC determinations, the value closest to the SBCE date was selected. Medications history including usage of aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) was made available for all patients. SBCE findings were analyzed against final diagnosis and FC values.
Results: Seventy adult patients were studied (53 females, 17 males). Three cases were excluded, due to capsule retention in the stomach. Median time from FC measurement to SBCE was 62 days. Twenty-three patients had normal FC (≤ 50 μg/g) and in all those the SBCE was normal. Forty-four patients had FC >50 μg/g; in this group, nine patients had FC between 51 and 100 μg/g and all had a normal SBCE. Thirty-five patients had FC levels >100 μg/g; of those, 15 (42.85%) had SBCE findings compatible with CD and mean FC levels 326 μg/g (range 116-1430 μg/g). A definitive clinical diagnosis of CD, based on subsequent follow-up, was made in 10/35 (28.5%) of patients. These 10 patients were within the subgroup of 15 patients with positive SBCE findings and had median FC levels 368 μg/g (range 235-1430 μg/g).
Conclusions: Measurement of FC levels prior to referral for SBCE is a useful tool to select patients with possible small bowel CD. A FC >100 μg/g is good predictor of positive SBCE findings, while FC >200 μg/g was associated with higher SBCE yield (65%) and confirmed CD in 50% of cases. Patients with FC between 50 and 100 μg/g had normal SBCE, despite symptoms suggestive of IBD. In all patients with clinical suspicion of CD and negative bi-directional endoscopies, FC assessment should be carried out prior to their referral for SBCE. Where FC is <100 μg/g (NPV 1.0), SBCE is not indicated.