Anti-serum protease (SP) binding in disease and control groups. (A) Activities of anti-SP IgG in all groups. Results (y-axes) were expressed as percentage binding of a positive control. Bars represent mean ± SEM (standard error of mean) (B) Correlation of anti-factor Xa (FXa) IgG activity with APLA IgG (aCL IgG and anti-β2GPI IgG) activity. Experiments were performed in duplicate for each sample. Results are representative of at least three independent experiments. GPLU, IgG phospholipid units; GBU, IgG β2GPI units.