The relationship of anticardiolipin antibodies to disease activity in systemic lupus erythematosus.

Sera from 124 blood donors, 60 rheumatoid arthritis (RA) and 57 SLE patients were measured for anticardiolipin antibodies by ELISA. Significantly raised IgG (aCLG) and IgM (aCLM) anticardiolipin antibody levels were found in RA and SLE (p less than 0.0005). However, in SLE both aCLG and aCLM levels were significantly higher than in RA (p less than 0.0025). We then conducted a transectional study to evaluate aCL levels and disease activity in SLE. There was a good positive predictive value (70%) between aCL and overall disease activity, but not for individual systems. A strong association between aCL and renal involvement irrespective of activity was also found (80%). Nine SLE patients fulfilled both the clinical and serological criteria for the antiphospholipid syndrome (APS) and a further 18 patients fulfilled the serological criteria for APS. Results indicate that aCL levels are of value in predicting overall disease activity in SLE and in monitoring those patients who fulfil or partially fulfil the criteria for APS.