Laboratory diagnosis of thrombophilic states: where do we stand?

Until recently the laboratory diagnosis of thrombophilia consisted on investigation of the plasmatic anticoagulant pathways and the search for dysfibrinogenemia and antiphospholipid antibodies/lupus anticoagulants. More recently, the laboratory investigation has been expanded by including activated protein C (APC) resistance, due or not to the presence of the factor V Leiden mutation; hyperprothrombinemia, due to the presence of the prothrombin mutation G20210A and hyperhomocysteinemia, due to impairment of the relevant metabolic pathway because of enzymatic and/or vitamin deficiency. Testing for thrombophilia may be useful for many reasons. First, the results of testing may provide valuable information to assess the risk of recurrence in the proband. Second, testing family members is useful for prophylactic and diagnostic purposes. Third, the identification of patients bearing combined defect helps to identify those at increased risk for thrombosis. Testing is recommended for patients with a past history of thrombosis and should be extended to their first-degree family members. Since most of the tests are not reliable during anticoagulation, it is preferable to postpone laboratory testing until after discontinuation of the treatment. Whenever possible testing should be performed by means of functional assays. DNA analysis is required for the prothrombin mutation G20210A. Laboratory diagnosis for antiphospholipid antibodies/lupus anticoagulant should be performed by a combination of tests including phospholipid-dependent clotting assays and solid phase anticardiolipin antibodies. Hyperhomocysteinemia may be assessed by high-pressure liquid chromatography methods, or by fluorescence polarization immunoassays.