VALUE OF ISOTYPE DETERMINATION OF SERUM ANTIBODIES AGAINST CHLAMYDIA FOR THE DIAGNOSIS OF CHLAMYDIA REACTIVE ARTHRITIS

In clinical rheumatology, the diagnosis of Chlamydia reactive arthriti s is difficult because an incomplete form of the disease can closely r esemble an undifferentiated seronegative mono/oligoarthritis. We inves tigated whether measuring specific isotypes of anti-Chlamydia antibodi es in serum can improve the diagnosis, by comparing such antibody conc entrations in the serum of patients with well-defined disease, i.e. Ch lamydia trachomatis sexually acquired reactive arthritis (CT-SARA), wi th other arthritides. Antibody levels were determined by enzyme-linked immunosorbent assay (ELISA). When considering two different isotypes and their combination, the best sensitivity (63%) was obtained for IgM and/or ISA results with a specificity of 81%. The patients with CT-SA RA and SARA had the highest levels of antibodies of all isotypes teste d. It is concluded that, in our experimental conditions, only very hig h values of specific isotypes could indicate a diagnosis of Chlamydia reactive arthritis.