Detection of Mycobacterium tuberculosis antigen in synovial fluid of patients with rheumatoid arthritis.

By use of antimycobacterial saline extract antibodies, Mycobacterium tuberculosis (MT) antigens have been detected in synovial fluid (SF) of patients with rheumatoid arthritis (RA) by a highly specific and sensitive double-antibody sandwich enzyme-linked immunosorbent assay (ELISA). Absorbance for 15 gout, 14 osteoarthritis (OA) patients, 12 patients with spondylarthropathies (SA) and eight patients with other inflammatory disorders (OID) ranged from 0.001 to 0.025 with the mean values of 0.0086 +/- 0.0078, 0.0077 +/- 0.0051, 0.0069 +/- 0.0059 and 0.0113 +/- 0.0059, respectively. Among 65 SF of patients with RA examined, 34 were found to be negative for MT antigen with absorbance ranging from 0.002 to 0.024 and a mean value of 0.0114 +/- 0.0070. For 31 (47.7%) MT antigen-positive specimens of RA, optical density ranged from 0.052 to 2.446 with a mean value of 0.5564 +/- 0.7354. Significant statistical difference (P less than 0.05) was found when MT antigen positives were compared with MT antigen negatives, gout, OA, SA and OID groups. Our results indicate that MT may be relevant to the pathogenesis of RA.