Laboratory evaluation for thrombophilias in children

Thrombophilia	Laboratory studies*
Factor V Leiden mutation	DNA-based PCR assay (or screen with functional assay for activated protein C resistance)
Prothrombin 20210 mutation	DNA-based PCR assay
Antithrombin deficiency	Antithrombin activity via chromogenic or clotting assay
Protein C deficiency	Protein C activity via chromogenic or clotting assay
Protein S deficiency	Free and total protein S levels measured via immunoassays
Antiphospholipid antibodies^¶	Immunoassays for IgG and IgM antibodies to cardiolipin and beta-2-glycoprotein-I and functional assay for the lupus anticoagulant phenomenon

This table summarizes our suggested approach to testing for thrombophilia in children. We suggest testing only for defects that are strongly associated with increased risk of VTE, which are listed in this table. Other tests that may be included on a "thrombophilia panel" but that we suggest not routinely performing include factor VIII level, homocysteine level, MTHFR variant testing, and lipoprotein(a) level. Refer to UpToDate topic on thrombophilia testing in children for further details of our approach.

PCR: polymerase chain reaction; IgG: immunoglobulin G; IgM: immunoglobulin M; VTE: venous thromboembolism; MTHFR: methylene tetrahydrofolate reductase gene.
* Refer to separate UpToDate content for details of laboratory testing for these disorders.
¶ Testing for antiphospholipid antibodies is performed only when evaluating children who have had a VTE. This testing is not part of the evaluation of asymptomatic children with a positive family history of VTE, because antiphospholipid antibody syndrome is an acquired rather than inherited thrombophilia.

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