0521779407-20 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:22
1424 Thrombophilia■Elevated homocysteine levels increase risk of atherosclerotic dis-
ease – risk is multiplied in patients with hypertension and in smokers.tests
Once thromboembolism has been diagnosed, the physician must
decide whether to screen for thrombophilic risks. About one third of
individuals with idiopathic thromboembolism will have a positive test
for thrombophilia.
In general, the following guidelines apply:
■Most patients should be screened for common disorders such as
Factor V Leiden and the Prothrombin gene mutation, the lupus anti-
coagulant, anticardiolipin antibodies, and hyperhomocysteinemia.
■Younger patients with unprovoked thromboses and/or a strong fam-
ily history of clots or patients with clots in unusual sites should be
screened for the more uncommon congenital and acquired disor-
ders.
■Hepatic vein thrombosis (Budd-Chiari syndrome) should also
prompt a search for paroxysmal nocturnal hemoglobinuria and my-
eloproliferative syndromes.Screening Laboratory Evaluation for Individuals with Venous
Thromboembolism
■Whole blood (heparin or ACD tube) for the following:
➣Genetic test for Factor V Leiden mutation
➣Genetic test for Prothrombin mutation
■Plasma (citrate tube):
➣Functional assay for AT (may be affected by heparin)
➣Functional assay for protein C (affected by warfarin)
➣Functional assay for protein S (affected by warfarin)
➣Immunologic assays for total and free protein S (can be affected
by estrogen use and pregnancy)
➣Screen for dysfibrinogenemia (immunologic and functional
assays for fibrinogen, thrombin time, reptilase time)
➣Clotting assays for lupus anticoagulant
➣Serologic tests for anticardiolipin antibodies
■Serum or plasma for the following:
➣Fasting homocysteine (Collect on ice and centrifuge within 1
hour)differential diagnosis
n/a