Fecal calprotectin as a biomarker of microscopic bowel inflammation in patients with spondyloarthritis

Aim: Microscopic bowel inflammation is present in up to 60% of all patients with spondyloarthritis (SpA) and appears to be associated with more severe joint disease and a higher risk of developing inflammatory bowel disease (IBD). This study aimed to determine the utility of fecal calprotectin (fCAL) in evaluating endoscopic and histological bowel inflammation in SpA patients.

Methods: Ileocolonoscopies with biopsies and fCAL measurements were performed in 65 patients with SpA.

Results: In 47 (72.3%) patients, the fCAL levels were higher than 50 μg/g, whereas in 20 (30.7%), these levels were greater than 250 μg/g. A total of 38 (58.5%) patients presented with microscopic bowel inflammation, and 13 (20%) presented with signs of endoscopic inflammation. fCAL levels were significantly higher in patients with microscopic bowel inflammation than in those without inflammatory findings (P < .001); additionally, these levels were slightly higher in patients with endoscopic signs of bowel inflammation (P = .053). A fCAL cutoff value of 96 μg/g predicted histological bowel inflammation with 73% sensitivity and 67% specificity. No statistically significant difference was observed in the fCAL levels between patients who had been treated or not treated with nonsteroidal anti-inflammatory drugs (NSAIDs).

Conclusion: Our findings confirm a high prevalence of microscopic bowel inflammation in SpA patients, regardless of the use of NSAIDs. The evaluation of fCAL levels proved to be useful in the identification of microscopic inflammation and could help in the more judicious indication of ileocolonoscopy. These results support the use of fCAL for the evaluation of microscopic bowel inflammation in SpA patients.