The US Department of Veterans Affairs (VA) now has a permanent pharmacogenomics service that provides genetic tests to give clinicians insight into the best medication options for their patients.
The tests, which have no extra cost, are available to all veterans, said pharmacist Jill S. Bates, PharmD, MS, executive director of the VA National Pharmacogenomics Program, who spoke in an interview and a presentation at the annual meeting of the Association of VA Hematology/Oncology .
Genetic testing is “a tool that can help optimize care that we provide for veterans,” she said. “Pharmacogenomics is additional information to help the clinician make a decision. We know that most veterans—greater than 90%—carry a variant in a pharmacogenomics gene that is actionable.”
The genetic tests can provide insight into the optimal medication for multiple conditions such as mental illness, gastrointestinal disorders, cancer, pain, and heart disease. According to a 2019 analysis of over 6 years of data, more than half of the VA patient population used medications whose efficacy may have been affected by detectable genetic variants.
For instance, Bates said tests can let clinicians know whether patients are susceptible to statin-associated muscle adverse effects if they take simvastatin, the cholesterol medication. An estimated 25.6% of the VA population has this variant.
Elsewhere on the cardiac front, an estimated 58.3% of the VA population has a genetic variant that increases sensitivity to the blood thinner warfarin.
Testing could help psychiatrists determine whether certain medications should not be prescribed—or should be prescribed at lower doses—in patients who’ve had adverse reactions to antidepressants, Bates said.
In cancer, Bates said, genetic testing can identify patients who have a genetic variant that boosts toxicity from fluoropyrimidine chemotherapy treatments, which include capecitabine, floxuridine, and fluorouracil. Meanwhile, an estimated 0.9% will have no reaction or limited reaction to capecitabine and fluorouracil, and 4.8% will have hypersensitivity to carbamazepine and oxcarbazepine.
Tests can also identify a genetic variant that can lead to poor metabolism of the chemotherapy drug irinotecan, which is used to treat colon cancer. “In those patients, you’d want to reduce the dose by 20%,” Bates said. In other cases, alternate drugs may be the best strategy to address genetic variations.
Prior to 2019, clinicians had to order pharmacogenomic tests outside of the VA system, according to Bates. That year, a donation from Sanford Health brought VA pharmacogenomics to 40 pilot sites. Since then, more than 88,000 tests have been performed.
The VA has now made its pharmacogenomic program permanent, Bates said. As of early September, testing was available at 139 VA sites and is coming soon to 4 more. It’s not available at another 23 sites that are scattered across the country.
A tool in the VA electronic health record now reminds clinicians about the availability of genetic testing and allows them to order tests. However, testing isn’t available for patients who have had liver transplants or certain bone marrow transplants.
The VA is working on developing decision-making tools to help clinicians determine when the tests are appropriate, Bates said. It typically takes 2 to 3 weeks to get results, she said, adding that external laboratories provide results. “We eventually would like to bring in all pharmacogenomics testing to be conducted within the VA enterprise.”