Clinical data from patients who were positive for anticardiolipin antibodies (ACAs), tested on a routine basis in an autoimmune laboratory, were obtained by questionnaires from the referring physicians. One hundred and sixty-two individuals had experienced a recent (within <6 months) thromboembolic event. All sera were tested for IgG and IgM antibodies against cardiolipin, β2-glycoprotein 1 (β2-glp 1), and the complex of phosphatidylserine/prothrombin (PPC) by in-house ELISA methods.
Among the 162 ACA-positive patients, 31 (19%) were also positive for antibodies against PPC. In the group with ACA only, 73% of the patients had no pre-existing rheumatic condition, compared with 32% in the PPC group (P = 0.00002). Thirty-two percent in the PPC group had SLE, vs 12% in the ACA group (P = 0.016). The fractions of patients with deep venous thrombosis (DVT), pulmonary embolism (PE), or myocardial infarction (MI) were equal, whereas cerebrovascular incidents (CVI) were more frequent among ACA patients; 51% vs 26% (P = 0.02). Antibodies against β2-glp 1 were also more frequent in the PPC group 61% vs 30% (P = 0.002).
Antibodies against both ACA and PPC seem to define a subset of patients with autoimmune thrombophilia. More patients with PPC antibodies had SLE and also tested positive for antibodies against β2-glp 1. The distribution of thrombotic manifestations differed between the two populations in that CVI was more frequent in the ACA-only group, whereas the fractions with DVT, PE, and MI were equal.