Investigation of asymptomatic intestinal inflammation in ankylosing spondylitis by fecal calprotectin.

Background And Study Aims: This study aimed to investigate the prevalence of intestinal inflammation in patients with ankylosing spondylitis (AS) by assessing fecal calprotectin (FC) levels and comparing them with those in patients with rheumatoid arthritis (RA) and non-inflammatory rheumatic diseases. Our secondary aim was to correlate FC levels with antirheumatic treatment, nonsteroidal anti-inflammatory drug (NSAID) usage, and disease activity measures.

Patients And Methods: This cross-sectional study included 97 patients with AS fulfilling the modified New York criteria, 48 patients with RA fulfilling the American College of Rheumatology criteria, and 49 patients with non-inflammatory rheumatic diseases. All patients were questioned about intestinal complaints, and symptomatic patients were excluded. Disease activity was measured in the AS and RA patient groups.

Results: The AS group had a significantly higher FC test positivity rate than the RA group (p = 0.016). Furthermore, the AS group had FC levels that were negatively correlated with disease duration (p = 0.04). FC levels were not correlated with any disease activity index, erythrocyte sedimentation rate, C-reactive protein, uveitis, or peripheral arthritis. Patients with AS who used NSAIDs had significantly higher FC levels than nonusers (p = 0.001).

Conclusions: This study revealed that 11% of patients with AS without intestinal complaints had elevated FC levels. FC levels were not correlated with disease activity in AS. Subclinical intestinal inflammation was higher in the early stages of AS. The AS group had a significantly higher FC test positivity than the RA group. In the AS group, NSAID users had significantly higher FC levels than nonusers; thus, no statistically significant difference was observed between biological agent users and nonusers.