[The possibilities for the early diagnosis of ankylosing spondylarthritis]

Soluble antigen HLA-B27 was assayed in blood serum of 30 patients afflicted with ankylosing spondyloarthritis (AS) and 25 healthy subjects having HLA-B27 (B27+) antigen in the phenotype. As compared to B27+ healthy subjects, B27+ patients with AS demonstrated a significantly higher level of soluble HLA-B27 antigen. A substance whose functional activity was found to be identical to that of soluble HLA-B27 antigen in blood serum of B27- patients with AS was discovered for the first time. It was absent from B27- healthy subjects. In addition to the identification of the fixed forms of soluble HLA-B27 antigen, the assay of this antigen in blood serum enhances the potentialities of laboratory diagnosis of AS, which plays an important role at the early disease stages.