Uncertainty Remains as to Whether Genetic Testing for VTE Improves Outcomes

Lisa Nainggolan

June 19, 2009

June 19, 2009 (Baltimore, Maryland) — There is insufficient evidence to conclude that genetic testing for two prothrombotic mutations improves outcomes for patients with venous thromboembolism (VTE) or for family members of people who carry the mutations, a new review has found [1]. Dr Jodi B Segal (Johns Hopkins University School of Medicine, Baltimore, MD) and colleagues report their findings in the June 17, 2009 issue of the Journal of the American Medical Association.

Clinicians test for genetic mutations in factor V Leiden and prothrombin G20210A--the two most common inherited risk factors for VTE--when treating patients who have had or are at risk of VTE, and such tests are widely offered in the US, with the FDA having approved the first tests for these mutations in 2003, Segal and colleagues explain. Segal told heartwire that she and her team were given the task of finding out how useful these genetic tests are in improving patient care, so they conducted a literature review.

But unfortunately, she explained, "We found that there really were no studies that tested that question. So we sought to answer the question by looking at intermediate steps along the way." Consequently, they were unable to provide any definitive conclusions, she said, adding that the Evaluation of Genomic Applications in Practice and Prevention (EGAPP) working group of the Centers for Disease Control and Prevention (CDC), which requested this review, would be making recommendations based on their report.

EGAPP's Dr Alfred Berg (University of Washington, Seattle) told heartwire : "We discussed in detail the review summarized in JAMA at our meeting this week in Atlanta.  A writing subcommittee is drafting the recommendation for presentation and vote at our October 5-6 meeting. I cannot comment on our conclusions or our recommendation at this time, because neither exists."

Tests Predict Recurrence, But Little Else

Segal said that in the absence of studies directly addressing the issue of whether genetic testing improved patient care, her team instead examined whether "the tests actually predict that there will be recurrent disease in these people or in their relatives, and whether treating patients with these mutations improves their outcomes. Those were the results we were able to report."

They included 46 articles in their review. They found that testing for factor V Leiden mutations "does predict recurrence, a little bit, although the odds ratios are not very high," she said, and "the prothrombin mutation appears to minimally predict recurrent disease, with the odds ratios being a little bit higher for family members than they were for those with incident disease."

In addition, she notes, "We also saw that there were studies demonstrating that treating patients with the mutations with anticoagulation does improve their outcomes, it does reduce the risk of recurrence, but probably to about the same extent as treating anybody who has had a VTE."

She said her team did not specifically address the issue of cost. "We would have reported on cost outcomes had we seen any, but we didn't. We did review some cost-effectiveness studies, but it's a little hard to know what to do with cost-effectiveness data if the test itself isn't remarkably effective."

"There is no direct evidence that testing for these mutations and the resultant management reduce VTE-related outcomes in individuals who have had VTE or in the probands' family members who have been tested," the researchers say. "We conclude that the incremental value of testing individuals with VTE for these mutations is uncertain."


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