Antithrombin (AT) and C1 inhibitor (C1INH) complexes, respectively, correlated with each other in systemic lupus erythematosus (SLE) patients. Complexes formed between activated FXII and FXI and the serpins AT and C1INH were measured by sandwich ELISA in plasma samples from SLE patients (n = 69). FXIIa-AT correlated with FXIa-AT (A), whereas FXIIa-C1INH correlated with FXIa-C1INH (B). Spearman’s r (r
) coefficients and P-values are given for each calculation.