The objective of this study is to determine whether patients with
systemic lupus erythematosus (SLE) and
anticardiolipin antibodies (ACA) have biochemical evidence of an ongoing prothrombotic state. Using a cross-sectional analysis of a cohort design in an outpatient SLE clinic setting, 43 consecutive patients with SLE participated. Patients underwent clinical and laboratory evaluations on two separate occasions at least 3 months apart. As part of the clinical evaluation, the following were ascertained: (1) the ongoing use of
warfarin therapy; (2) the presence of prior venous and arterial thromboembolic disease by history, critical review of objective tests, and examination for reflux in the deep veins of the legs as an
indicator of
venous thrombosis; and (3) disease-related activity by performing a lupus activity criteria count (LACC). As part of the laboratory evaluation, blood was taken on both occasions and assayed for
prothrombin fragments (F1 + 2) and
fibrinopeptide A (FPA), as indices of
thrombin generation and activity, respectively, and ACA. For the analyses, patients were classified as ACA+ if the assay was abnormal on both occasions and ACA- if the assay was negative on both occasions or negative on one occasion and positive on the other. ACA+ patients had: (1) a significantly higher mean level of F1 + 2 (1.07 nmol/L) than ACA- patients (0.79 nmol/L; P = .02) and patients receiving
warfarin (0.47 nmol/L; P = .009) and (2) a significantly higher mean level of FPA (1.01 nmol/L) than ACA- patients (0.45 nmol/L; P = .02). When patients with prior
thromboembolism were excluded from the analysis, significant differences in the mean levels of F1 + 2 and FPA between ACA+ and ACA- patients were still seen, whereas when patients with prior
thromboembolism and/or active disease were excluded from the analysis, a significant difference in the mean level of FPA and a nonsignificant trend in the mean level of F1 + 2 were seen. The results of this study support the hypothesis that the presence of ACA in SLE patients is associated with an ongoing prothrombotic state.