Comparative prevalence of antiphospholipid antibodies and thrombophilic genotypes in consecutive patients with venous thrombosis.

The prevalence of antiphospholipid antibodies (aPL) and thrombophilic genotypes was compared and their reciprocal interactions assessed in consecutive patients with venous thrombosis (n = 101; 58 male, 43 female; mean age, 56 +/- 16 years) and in blood donors (n = 121; 55 male, 46 female; mean age, 43 +/- 12 years). Multiple aPL were detected by enzyme-linked immunosorbent assay (ELISA) and factor V Leiden (FVL), methylenetetrahydrofolate reductase (MTHFR) C-677 --> T and prothrombin (PT) G(21210) --> A by polymerase chain reaction. A pro-thrombotic state, including aPL, was found in 81% (82/101) of patients and 23% (29/121) of controls (P < 0.0001, odds ratio = 13.69, 95% confidence interval = 7.14-26.25). The prevalence of total aPL-positives was lower than MTHRF+/+ (homozygous state), FVL and PT G(20210) --> A (P < 0.0001) in the control group, but in line with the prevalence of total thrombophilic genotypes in the patient group: MTHFR+/+, 29%; FVL, 19%; PT, 14%; aPL, 20%. Having variously combined aPL and thrombophilic genotypes, only aPL remained as the most common pro-thrombotic factor in the patient group (P = 0.003). In patients without circumstantial factors for thrombosis, carriers of MTHFR+/+ + aPL showed a lower age at event than carriers of MTHFR+/+ alone or aPL alone (38 +/- 24 versus 65 +/- 10 years, P < 0.05 and 38 +/- 24 versus 63 +/- 16 years, P < 0.05, respectively). In the same patients, mean plasma homocysteine measured by an ELISA method was significantly higher in the MTHFR+/+ + aPL group than in the MTHFR+/+ alone or aPL alone groups (P = 0.01). Antiphospholipid antibodies are as common as thrombophilic genotypes in patients with venous thrombosis, and the interaction of aPL with MTHFR+/+ may influence age at first event via elevated plasma homocysteine. Blood Coagul Fibrinolysis 12:659-665 (C) 2001 Lippincott Williams & Wilkins.