When are screening tests indicated for coagulation-promoting nonplatelet hemostatic disorders?

Updated: Oct 28, 2019
  • Author: Muhammad A Mir, MD, FACP; Chief Editor: Perumal Thiagarajan, MD  more...
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Answer

Laboratory screening for aPCR is performed by functional tests measuring the effect of aPC on aPTT in plasma containing a heparin neutralizer. Second-generation tests that reduce screening errors are now available. [62]

The question of who should be screened remains unsettled. Marz et al have taken an inclusive approach to causes of venous thromboembolism (VTE) in describing the interactions between genetic and environmental causes of this disease state. [63] They propose that inborn factors that cause a predisposition to thrombosis are present in most patients who develop VTE.

The relatively rare defects of antithrombin III, protein C, and protein S deficiencies are found in 15-20% of thrombophilic families, in contrast to the common genetic polymorphisms of procoagulant molecules, factor V Leiden, and the prothrombin 20210 A allele. The results of Marz and colleagues' studies of factor V Leiden and prothrombin 20210 A indicate that many symptomatic individuals have more than one (genetic and/or environmental) risk factor. Important nongenetic risk factors include age, tissue damage, oral contraception, pregnancy, obesity, and lack of physical activity.

A thrombophilia workup including the above-discussed laboratory tests is warranted only in young patients with unusual sites of first thrombosis, to decide duration of anticoagulation, use of oral contraceptives, and family counseling. Indiscriminate testing is not warranted.


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