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AHRQ Report Finds 'Insufficient Evidence' Supporting Genetic Testing To Prevent Deep-Vein Thrombosis

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The Department of Health and Human Services' Agency for Healthcare Research and Quality has found "insufficient evidence" to conclude that genetic testing for two gene mutations in adults with a history of blood clots helps to prevent a condition known as deep-vein thrombosis or to improve other clinical outcomes.

AHRQ's investigations also "failed to find any benefit from genetic testing of family members of patients who have at least one of the two mutations — Factor V Leiden (FVL) and prothrombin G20210A — as well as a history of deep-vein thrombosis," the agency said in a statement.

A summary of the report, titled "Outcomes of Genetic Testing in Adults with a History of Venous Thromboembolism," will be published in the June 17 issue of JAMA.

The study authors — led by Jodi Segal, of the AHRQ-supported Johns Hopkins Evidence-based Practice Center in Baltimore, Md. — recommend conducting randomized trials with "sufficiently large sample sizes and long-term follow-up," in addition to other types of research to determine whether genetic testing in patients with a history of blood clots improves outcomes and whether physicians should alter current treatment practices to adopt genetic testing for the prevention of deep-vein thrombosis.

"While genetic testing shows great promise to improve treatment and prevent disease, this report clearly shows that we need more research and evidence to achieve its full potential," AHRQ Director Carolyn Clancy said in a statement. "But people can help reduce their likelihood of developing a blood clot by talking with their doctor about precautions."

In their investigations, authors also reviewed published literature for the accuracy of the testing methods used to identify the FVL and prothrombin G20210A mutations, which can signal continued risk of blood clots. The literature showed that while these assays have high analytic validity and laboratories test for these mutations accurately, "the test results have variable clinical validity for predicting venous thromboembolism in these populations and have only weak clinical utility," the authors concluded in the report.

The study authors looked at nearly 8,000 published articles on the analytic validity, clinical validity, and clinical utility of genetic tests for venous thromboembolism and pooled the results in 124 articles addressing the primary endpoint on whether genetic testing improves outcomes.

The study authors did not find any studies that directly addressed the effect of genetic testing on patient outcomes. However, study authors were able to identify research indicating that keeping patients who have a genetic tendency to develop blood clots on anticoagulants, such as warfarin, reduces the chance of future clots. "This benefit appears to be similar to that seen in patients who do not have the genetic tendency to develop blood clots but who have a history of clots," AHRQ said in a statement.

AHRQ researchers found one study that supported the hypothesis that clinicians should change disease management based on genetic test results. "There was high-grade evidence that anticoagulation reduces recurrent events in probands with FVL or prothrombin G20210A; however, there was low-grade evidence that the relative reduction with treatment is comparable to that seen in individuals without mutations," the study authors reported. "There was moderate evidence to support the conclusion that neither harms nor benefits of testing have been demonstrated conclusively.

"Decision-analysis models suggest that testing may be cost-effective in select individuals," the study authors noted.

As many as 600,000 living in the US suffer form blood clots that form in the legs or pelvis, a condition known as deep-vein thrombosis. The condition occurs commonly in sedentary people recovering from surgery or traveling long distances. Deep-vein thrombosis sufferers are at risk of pulmonary embolism, which can be fatal in some. According to AHRQ data on hospital patients, 258,000 individuals were diagnosed with pulmonary embolism in 2006, and 20,000 died from the condition.

AHRQ's evidence report was requested by the Office of Public Health Genomics at HHS' Centers for Disease Control and Prevention. The Evaluation of Genomic Applications in Practice and Prevention Working Group, established by OPHG in 2005, will use this report in addition to other evidence to make recommendations on the validity and utility of genetic tests for FVL and prothrombin G20210A.

This report is the fifth evidence report requested for EGAPP. The working group has issued recommendations for SSRI genetic testing, ovarian cancer detection and management, gene expression profiling in breast cancer, genetic testing for lynch syndrome in colorectal cancer patients, and testing for UGT1A1 in colorectal cancer patients treated with irinotecan.

In most of its reviews, EGAPP has found limited evidence supporting genetic testing. However, the working group did find sufficient evidence that genetic testing for Lynch syndrome in individuals with newly diagnosed colorectal cancer reduces morbidity and mortality in relatives, and recommends this intervention.

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