Fluctuations of anticardiolipin antibody levels in patients with systemic lupus erythematosus: a prospective study.

In 53 patients with systemic lupus erythematosus sequential blood samples obtained during a four year period (range 6-47 months) were screened for anticardiolipin antibodies (ACAs). Disease activity and treatment with prednisone were also assessed and related to ACA concentrations. During follow up only 21 patients for ACA IgG (40%) and 25 for ACA IgM (47%) remained in the ACA category (negative, low positive, high positive) found at the first sample taken at entrance. Marked increases from negative to high positive concentrations were sometimes seen and were not accompanied by typical events such as thrombosis or thrombocytopenia (the ACA syndrome). Shifts in ACA concentrations could not always be explained by changes in prednisone dose. Also, in patients with low dose prednisone treatment or none at all (n = 22) 10 patients (45%) changed ACA IgG category and 12 patients (55%) fluctuated in ACA IgM categories during follow up. As a consequence of the variability in ACA titres relations of ACAs with the ACA syndrome depended on the blood sample studied. In the second sample, randomly taken half way through follow up, no significant relations with the ACA syndrome could be found. Anticardiolipin antibody IgG was significantly associated with disease activity in 11/47 patients (23%) and in the group as a whole. During remission ACA IgG was significantly associated with the ACA syndrome, whereas during moderate/severe disease activity in the same patients that correlation was not significant. Anticardiolipin antibody IgM was much less influenced by disease activity, and in only 4/47 patients (9%) could a significant relation with disease activity be shown. Associations of ACA IgM with the ACA syndrome were significant during both lupus flares and remission.