Appropriate Hypercoagulable Testing

EFFECTS OF ANTICOAGULANT THERAPY ON HYPERCOAGULABLE TESTING
AND OTHER ISSUES AFFECTING RESULTS from Institute of Transfusion Medicine, by Irina Chibisov, MD. 2012.

SUMMARY
Many factors interfere with results and interpretation of hypercoagulable studies. When possible, hypercoagulable testing should be done outside of an acute event, including thrombosis, infection, inflammation, and most definitely prior to the initiation of anticoagulation therapy.

Factor V and prothrombin DNA testing is fairly definitive.  Test results for protein S, C, and antithrombin III deficiencies are more difficult to interpret as environmental factors can influence the results. Clinical and family history should always be used to aid in testing interpretation. It is important to rule out acquired protein S, C, and antithrombin III deficiency prior to establishing a diagnosis.

Treatment with Coumadin can interfere with protein C and S testing. Ideally, Coumadin use should be held for two weeks prior to undergoing these tests. Alternatively, heparin use can replace the Coumadin during that time frame. Acquired protein S deficiency is quite common, frequently caused by factors such as pregnancy, liver disease, inflammatory conditions, and thromboembolism.

Acquired antithrombin deficiency can result from mild liver disease, acute thrombosis, nephrotic syndrome, and heparin anticoagulant therapy. Protein S assays are not reliable during pregnancy and heparin therapy can result in a false positive antithrombin III test result; but, antithithrombin III can be checked on Coumadin.

It is always important to remember that protein C, S, and antithrombin III congenital deficiencies are rare and should be suspected in strongly thrombophilic patients: i.e., those with a venous thromboembolism prior to age 50, recurrent venous thromboembolism, or with an extensive family history of thrombosis. When results are borderline, repeat testing and comparative studies of other family members can be appropriate.

Finally, direct thrombin inhibitors cause significant interference with all functional coagulation assays and hypercoagulable testing should not be ordered inpatients on these agents.

INCOMPLETE - needs to be edited to be more blog-friendly & clinically applicable. Case?