Education Blog for Healthcare Professionals

Family Member Testing For Thrombophilia


If a thrombophilia (clotting disorder) has been identified in a patient with blood clots (venous thromboembolism = VTE), the question arises whether other family members should be tested for the same thrombophilia.

My Clinical Approach

My approach in clinical practice to thrombophilia testing in family members is summarized in table 1: Family Member Testing. If the patient has a “strong” inherited thrombophilia (i.e. homozygous factor V Leiden, homozygous prothrombin 20210 mutation, double heterozygous factor V Leiden plus prothrombin 20210 mutation, deficiency of protein C, S or antithrombin) then I consider and discuss testing of other family members. However, if the patient only has heterozygous factor V Leiden or heterozygous prothrombin 20210 mutation, I do not recommend testing of family members, as the finding of one of these “mild” thrombophilias typically has no impact on management of family members also affected by one of those “mild” thrombophilias.

Finding of a “strong” thrombophilia in an unaffected family member barely ever leads to the recommendation to start long-term “blood thinners”, if the person never had a blood clot. However, the reason I consider testing for a “strong” thrombophilia in family members is that finding a “strong” thrombophilia may lead to different treatment recommendations in certain circumstances: a) a “blood thinner” before long-distance travel; at times of non-major surgeries, such as arthroscopic knee surgery, or leg immobilization with a cast; during pregnancy or after delivery; and (b) longer-term VTE prevention with “blood thinners” for a few weeks after surgical procedures or hospital admissions where usually only short-term prophylaxis is given.


Existing Guideline

A Jan 2011 guideline from the “Evaluation of Genomic Applications in Practice and Prevention” (EGAPP) Working Group recommends “against routine testing for factor V Leiden and/or the prothrombin 20210 mutation in asymptomatic family members of patients with VTE with factor V Leiden or prothrombin 20210>A mutation for the purpose for considering primary prophylactic anticoagulation” (ref 1). I agree with this recommendation, as long as it is clear to the reader that this statement is referring to primary long-term prophylaxis with “blood thinners”, i.e. the staring of anticoagulation in a person who has never had a blood clot (ref 2). However, the guideline does not provide guidance regarding potential thrombophilia testing for factor V Leiden and the prothrombin 20210 mutation for the purposes of helping with decision makings in the scenarios listed above: times of non-major surgeries, limb immobilization due to casts, pregnancy and the 6 weeks after delivery, long distance travel.


  1. Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Working Group. Recommendations from the EGAPP Working Group: routine testing for factor V Leiden (R506Q) and prothrombin (20210>A) mutations in adults with a history of idiopathic venous thromboembolism and their adult family members. Genet Med 2011:13:67–76.
  2. Moll S. Who should be tested for thrombophilia? Genet Med 2011:13:19-20.

For Patients

This same post, written for patients, can be found here.

Disclosure: I have no financial conflict of interest relevant to this blog entry.

Last updated: Feb 2nd, 2011

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