Primary Sjögren's syndrome (pSS) is a systemic rheumatic disease in which gastrointestinal (GI) symptoms are common. Faecal calprotectin (FC) is a non-invasive biomarker that has been suggested to discriminate organic intestinal disease from functional disorders. The purpose of this study was to explore the usefulness of FC testing in patients with pSS.
In total, 56 consecutive patients with pSS and 29 healthy control subjects were included in this cross-sectional study. FC was measured with a commercially available enzyme-linked immunosorbent assay kit. GI symptoms were evaluated with the Rome III questionnaire and the Visual Analogue Scale for Irritable Bowel Syndrome. In patients with pSS, disease activity was estimated using the European League Against Rheumatism (EULAR) Sjögren's Syndrome Disease Activity Index (ESSDAI), and patient-reported outcomes were evaluated with the EULAR Sjögren's Syndrome Patient-Reported Index.
Patients with pSS had higher levels of FC than healthy control subjects (median 54 μg/g, interquartile range [IQR 20-128]; vs. 20 μg/g [20-43]; p = 0.002). Concomitant organic GI disease was found in 14 patients with pSS and included inflammatory bowel disease (n = 3), colonic adenoma (n = 2) and GI lymphoma (n = 1). Patients with organic GI disease had higher FC levels than the other patients with pSS (median 274 μg/g [IQR 61-363] vs. median 34 μg/g [IQR 20-76]; p < 0.001). Although patients with pSS reported abdominal discomfort more frequently than healthy control subjects did, such symptoms were not associated with organic GI disease or elevated FC levels. FC correlated moderately with ESSDAI. Excluding patients with organic GI disease, we did not identify any significant association between ESSDAI and FC levels.
GI symptoms are frequent in pSS. Contrary to patient-reported outcomes, elevated FC levels in pSS indicate possible organic GI disease that warrants further investigation.