Inflammatory bowel disease-associated antibodies in ankylosing spondylitis: relationship with clinical and laboratory markers of inflammation

Background/Purpose. To study the relationship between levels of antibodies associated with inflammatory bowel diseases (IBD) and inflammatory markers in ankylosing spondylitis (AS). Materials and methods. The sera of 44 healthy donors (HD) and 51 patients with AS were studied: 40 men, 11 women aged 44.0 (34.0–49.0) years with a disease duration of 12.0 (5.0–20.0) years, high disease activity (BASDAI – 5.3; 4.5–6.4; ASDAS ESR – 3.6; 3.0–4.4; ASDAS CRP – 3.7; 2.8–4.5). IBD was diagnosed in 22 % of patients with AS. IgG/IgA antibodies to S. cerevisiae (ASCA), IgG/IgA antibodies to glycoprotein 2 (GP2), IgG antibodies to cathepsin G, elastase, serum calprotectin (sCP), interleukin-6 (IL-6) were determined by ELISA. Results. Patients with AS without IBD and AS with IBD had higher levels of IgA ASCA, IgA aGP2, and elastase antibodies than HD (4.5; 2.6–6.4 U/ml and 4.9; 3.7–7.3 U/ml vs 1.9; 0.6–2.6 U/ml, p=0.0008, p=0.001; 1.2; 0.8–5.5 U/ml and 1.2; 0.9–11.8 U/ml vs 0.7; p=0.007, p=0.02; 8.2; 5.9–9.9 U/ml and 9.1; 8.5–10.5 U/ml vs 5.6; 4.7–8.3 U/ml, p=0.01, p=0.003). The concentration of antibodies to cathepsin G was higher in AS with IBD compared to AS without IBD (0.8; 0.5–1.0 U/ml vs 0.4; 0.3–0.6 U/ml, p=0.02). The levels of IgA ASCA correlated with IL-6 (r=0.3), IgA aGP2 – with sCP (r=0.3), antibodies to elastase – with ESR (r=0.4), antibodies to cathepsin G – with ESR (r=0.4) and BASDAI (r=0.4) (p