Thrombophilia laboratory findings

Revision as of 19:02, 29 June 2016 by Asiri Saumya Ediriwickrema (talk | contribs) (update)
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Asiri Ediriwickrema, M.D., M.H.S. [2]

Overview

  • There are specific laboratory findings associated with each inherited thrombophilias.
  • Refer to page on screening for recommendations regarding thrombophilia testing.

Laboratory Findings

Timing

The timing of tests is very important as it influences the levels of various thrombogenic factors in the body.

  • Testing at the time of acute venous thrombosis is not indicated or during ongoing anti-coagulation.
  • Best time to test is 4 weeks after completion of anticoagulation.
  • Avoid intercurrent severe illness
  • Pregnancy, oral contraceptives, hormone replacement therapy and cancer chemotherapy may also affect some tests.
  • Factor V Leiden and Prothrombin mutation can be done in patients on anticoagulants and even in acute phase, as these are PCR tests. However, other tests can be done only at a later stage to rule out two disorders.

Type of tests

Tests for thrombophilia are categorized according to their priority, as discussed below:

Priority Timing Test Associated Diagnosis
High Complete blood count General
Coagulation studies: INR, prothrombin time, partial thromboplastin time General
Factor V Leiden mutation studies Factor V Leiden
Prothrombin 20210 gene mutation Prothrombin G20210A
Lupus anticoagulant Antiphospholipid syndrome
Intermediate Anticardiolipin antibodies Antiphospholipid syndrome
Delay 6 months Functional assay for antithrombin (antithrombin-heparin co-factor assay) Antithrombin deficiency
Delay 6 months Protein C functional assay (preferred over plasma protein levels) Protein C deficiency
Delay 6 months Free protein S immunoassay Protein S deficiency
Factor VIII level (use c-reactive protein as control) Factor VIII disorders
Flow cytometry Paroxysmal nocturnal hemoglobinuria
Peripheral blood smear, JAK2 mutation studies Myeloproliferative disorders
Homocysteine level Hyperhomocysteinemia
Vitamin B12 level Hyperhomocysteinemia
Low Thrombin time General/Fibrinogen disorders
Fibrinogen level Fibrinogen disorders
Reptilase time General/Fibrinogen disorders
Plasminogen level Plasminogen disorders
Factor IX activity Factor IX disorders
Factor X activity Factor X disorders

Variability in thrombophilia testing

  • Warfarin: Decreases protein C and S levels
  • Heparin: Decreases antithrombin activity and interferes with evaluation for antiphospholipid antibody
  • Acute thrombosis: Decreases antithrombin, protein C, and protein S levels

References

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