ADA were detected in 11 (26.2%) patients (7/27 (25.9%) AS, 3/10 (30%) undifferentiated SpA and 1/2 (50%) SpA related to IBD) during treatment with the first anti-TNF drug and were more frequent in patients treated with Ifx (9 (81.8%) with Ifx, 2 (18.2%) with Ada, 0 (0%) with Etn, p = 0.006). Here, TNF is linked to inflammatory bowel disease.