Value of anticardiolipin antibodies for monitoring disease activity in systemic lupus erythematosus and other rheumatic diseases.

The prevalence of anticardiolipin antibodies in active systemic lupus erythematosus (SLE) was compared with that in inactive SLE and other rheumatic and non-rheumatic diseases to determine the value of these autoantibodies in monitoring rheumatic diseases. Pairs of IgG- and IgM-aCL were measured by ELISA in 173 consecutive hospitalised patients, including 141 with rheumatic diseases (18 active SLE, 21 inactive SLE, 19 rheumatoid arthritis, 13 reactive arthritis, 7 other spondyloarthropathies, 16 vasculitis, 47 other autoimmune diseases) and 32 non-rheumatic controls. A further 101 aCL pairs were determined during follow-up in 19 patients with SLE. Serum concentrations were analysed with respect to SLE activity and compared between the different patient groups. IgG- and IgM-aCL levels in excess of 10 GPL and 9 MPL respectively were considered positive. 30.6% of all patients (53/173) were found to be positive for IgG-aCL, as against only 9.8% (17/173) for IgM-aCL. IgG-aCL serum levels in active SLE differed significantly from all other groups, including inactive SLE (all p < 0.005). Median IgM-aCL levels were below the cut off point in all groups, although measurable values were obtained almost exclusively in active SLE and RA. In this study IgM-aCL measurement was of less value in monitoring rheumatic diseases. IgG-aCL positivity in SLE was associated with a significantly higher odds ratio (OR) for active disease (OR 16.0, 95% confidence interval: 2.8-90.0). The results show that disease activity in SLE was accompanied by significantly increased IgG-aCL, whereas no elevation was found in other diseases. This parameter may therefore be useful in monitoring SLE activity.