Seasonal distribution of antiphospholipid antibodies

Background and Purpose-The purpose of this study was to determine if there was a seasonal variation in antiphospholipid antibody (aPL) titers and whet her this variation differed between stroke cases and control subjects. Methods-IgG and IgM anticardiolipin and antiphosphatidyl serine antibody ti ters were obtained on serum samples from 884 stroke patients and 1024 contr ol subjects over a 7-year period. Temporal distributions by month of blood draw were evaluated. Results-Marked seasonal differences in the proportion of positive titers we re found for control subjects, but no seasonal variability among patients w as noted. In control subjects, positive titers occurred less frequently in the summer months, mirroring the seasonal trends seen in respiratory track infections and rheumatic fever. Conclusions-Our data suggest some aPL antibodies arise from different origi ns in patients and control subjects. The seasonality observed in the appare ntly normal population may be related to antibodies of infectious origin an d is consistent with the reported lack of association with thrombosis of in fection- related antibodies.