Venous thrombosis: prevalence of prothrombotic defects in north Indian population.

431 patients with thrombosis of different venous system were evaluated for underlying acquired and inherited prothrombotic states. Associated acquired risk factors were observed to be present in 28.7% patients and possible inherited in 32.3%, in the rest, no cause could be identified. Major acquired risk factors included coexistence of liver disease (12.2%), oral contraceptives (4.1%), puerperium (2.5%), malignancy (2.3%) and lupus anticoagulant (2%). Low levels of protein C were detected in 21.1% and of which 11.3% were attributed to acquired factors. Protein S deficiency was found in 19.0% and of these 10.4% cases were associated with acquired risk factors. Antithrombin III (AT III) deficiency was detected in 6.4% of patients, of which 4.8% were secondary to acquired factors. In the rest, deficiency of protein C, protein S and AT III were attributed to inherited factors as no associated acquired risk factor was present. Activated protein C resistance (APC-R) was present in 12.5% cases.