Genetic testing for inherited blood-clotting abnormalities is not routinely recommended for patients with venous thromboembolism (VTE) of unknown cause, according to a new expert panel statement in a recent issue of Genetics in Medicine, the official peer-reviewed journal of The American College of Medical Genetics (ACMG). The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.
Available tests can identify genetic abnormalities responsible for clotting disorders that can cause VTE. However—since the treatment is often the same whether or not a gene abnormality is present—these tests aren't necessary for most patients with VTE, concludes the latest statement by the Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Working Group.
Evidence Doesn't Support Benefits of Routine FVL or PT Gene Testing
Genetic abnormalities involving factor V Leiden (FVL) and the prothrombin (PT) gene can cause inherited blood clotting disorders. These conditions, called thrombophilias, can result in potentially serious VTEs: clots that block blood flow in the legs (deep vein thrombosis) or lungs (pulmonary embolism). Simple gene tests can detect FVL or PT abnormalities causing inherited thrombophilias.
However, these thrombophilias aren't the only cause of VTEs. Many other conditions can cause or place patients at increased risk of VTEs—for example, surgery or pregnancy. In these situations, since the likely cause is known, gene testing is unnecessary. The new statement was developed to provide physicians with research-based recommendations to help in deciding when FVL/PT testing provides useful information for patient care.
Based on the available data, the EGAPP Working Group concludes that routine FVL and PT testing is not recommended for adult patients with VTE—even in the absence of any known cause or risk factor. It's true that testing could identify patients with FVL or PT abnormalities, who are at increased risk of a recurrent VTE. However, whether or not a mutation is present, the recommended treatment is the same: long-term therapy with anticoagulant (blood thinner) drugs.
Furthermore, testing is not routinely recommended for unaffected family members of patients with VTE. Again, the test results wouldn't lead to any change in treatment: even if the family members had a mutation that increased their future risk of VTE, they would not be treated with anticoagulant drugs. That's because the risk of bleeding complications from blood-thinning drugs would outweigh the possible benefits of reducing their risk of VTE.
Based on the quality of the supporting evidence, the strength of the new recommendation on FVL/PT testing is rated "moderate." The statement draws no conclusions about FVL and PT testing in other, less-common situations; or in patients with other factors that may affect VTE risk, such as oral contraceptive use.
In an accompanying editorial, Dr. Stephan Moll of University of North Carolina School of Medicine, Chapel Hill, emphasizes that the new report only recommends against "routine" testing. For certain groups of patients and family member, FVL/PT testing may indeed be justified. Dr. Moll writes, "Testing selected patients with unprovoked VTE may be beneficial; testing everybody with unprovoked VTE is, indeed, not useful."
Dr. Moll adds that ongoing research may soon identify more refined approaches to assessing individual clotting risk, making the focus on specific gene disorders less relevant. The January issue also includes a thorough review and update on FVL thrombophilia, authored by Dr. Jody Lynn Kujovich of the Northwest Cancer Specialists, Portland, Ore.
The EGAPP initiative was developed by the National Office of Public Health Genomics at the Centers for Disease Control and Prevention, with the goal of supporting evaluation of genetic tests and other genomic applications that are in transition from research to clinical and public health practice. The independent EGAPP Working Group bases its recommendations on commissioned, systematic reviews of available studies addressing the validity and utility of specific types of genetic tests. These reviews follow the most up-to-date methods for collecting, analyzing, and grading evidence on analytic and clinical validity and on the clinical utility of genetic and genomic tests.