Increasing of SIgA serum levels may reflect subclinical intestinal involvement in non-radiographic axial and peripheral spondyloarthritis.

The results show that pSpA as well as nr-axSpA share a similar SIgA-intestinal involvement independently of a previous infection. This suggests that serum SIgA increases are evidence of subclinical intestinal compromise which could have influence on disease activity but not in this progression. Key Point • The levels of SIgA, IgA against some enteric bacteria, and IL-17, IL-21, and IL-6 are correlated with clinical features in a group of SpA patients.