Thrombophilia laboratory findings
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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[1].
- Refer to page on screening for recommendations regarding when to pursue thrombophilia testing.
Laboratory Findings
Variability in thrombophilia testing
- Warfarin decreases protein C and S levels.
- Heparin decreases antithrombin activity and lead to false positive results for lupus anticoagulant.
- Direct acting oral anticoagulants can interfere with evaluation for lupus anticoagulant, antithrombin activity, protein C, and S levels.
- Acute thrombosis: Decreases antithrombin, protein C, and protein S levels.
Timing
- Given the variability discussed above, timing is important to accurately evaluate for certain thrombophilic states[2][3].
- Acute thrombosis can affect levels of coagulation factors, therefore, testing should be delayed for approximately six months.
- Anticoagulation can affect certain tests, and should be completed approximately four weeks after completion of anticoagulation.
- Avoid testing during 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 genetic (PCR) tests.
Type of tests
Tests for thrombophilia are categorized according to their priority, as summarized below.
- High priority testing should be conducted if screening conditions are met.
- Intermediate and low priority testing should be completed in the approprate clinical context.
| 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 | ||
| 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 | |
| Intermediate | 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 |
References
- ↑ Seligsohn U, Lubetsky A (2001). "Genetic susceptibility to venous thrombosis". N Engl J Med. 344 (16): 1222–31. doi:10.1056/NEJM200104193441607. PMID 11309638.
- ↑ Cohoon KP, Heit JA (2014). "Inherited and secondary thrombophilia". Circulation. 129 (2): 254–7. doi:10.1161/CIRCULATIONAHA.113.001943. PMC 3979345. PMID 24421360.
- ↑ Stevens SM, Woller SC, Bauer KA, Kasthuri R, Cushman M, Streiff M; et al. (2016). "Guidance for the evaluation and treatment of hereditary and acquired thrombophilia". J Thromb Thrombolysis. 41 (1): 154–64. doi:10.1007/s11239-015-1316-1. PMC 4715840. PMID 26780744.