ATLANTA — Wafarin, like other blood thinners are very tricky medications. Oftentimes it takes weeks, sometimes months to get a patient on a steady dose. A great bit of it is actually due to trial and error, which can be taxing to the patient and also lead to hospitalization.
But according to results from the Medco-Mayo Wafarrin Effectiveness Study presented at the American College of Cardiology (ACC; Washington) 59th annual scientific session, a new genetic test will alleviate the dosing issue and help to significantly reduce the number of hospitalization.
Mayo Clinic (Rochester, New York) along with Medco Health Solutions, (Franklin Lakes, New Jersey) headed up the study.
Results proved that hospital admissions were cut by one third, for either excess bleeding or unwanted bloodclotting.
The assay tests for variations in two key genes that strongly influence the patient's sensitivity to the blood thinner warfarin.
“We found that the closer to the warfarin dosage the genotyping was done, the better the outcome,“ Robert Epstein, CMO and president of the Medco Research Institute, said during a Tuesday morning press conference. “We found that there was a nearly 30% reduction in a six-month period for people using the genotype.“
For the study, researchers recruited 896 patients who were beginning warfarin therapy. All study participants were members of a prescription benefits plan managed by Medco Health Solutions. They came from 49 of 50 states and a variety of practice settings.
Shortly after starting warfarin therapy, patients gave a blood sample or a cheek swab, which was analyzed at the Mayo Clinic For each patient, the ordering physician received a report on the genetic expression of two genes, CYP2C9 and VKORC1, as well as clinical information on how to interpret the findings.
According to information presented on the study at the conference, a patient might be classified as having a high sensitivity to warfarin based on genotype. In this case, the physician would be advised to reduce the warfarin dose and monitor blood tests more frequently. If a patient were found to have a low sensitivity to warfarin, the report would recommend an increase in warfarin dose. Each physician was free to decide how to respond to the report and what action to take.
Patients in the gene-testing group were also 29% less likely to be hospitalized for bleeding or thromboembolism. The study's findings were even stronger when the analysis included only hospitalizations that occurred after genotyping. In this per-protocol analysis, patients who underwent genetic testing had a 33% lower risk of all-cause hospitalization and a 43% lower risk of hospitalization for bleeding or thromboembolism.
But in order for patients to get the maximum effect and benefit from the test it must be taken at the beginning of dosing.
Questions arose if the test, which carries a $400 price tag, was truly worth it.
“If we're able to reduce the hospitalization it would be more than $400,“ Epstein said. “Warfarin's been used for 50 years in this country but we still see a 22% hospital rate in the first six months of using.“
He added that if a patient is already stable on the medication, that the test probably isn't needed.
“If you're on a stable dose you don't need the genotyping test,“ Epstein said.
To date, there are about two million people that use warfarin therapy each year in the U.S. to prevent unwanted blood clots in certain high-risk medical conditions, such as atrial fibrillation or following surgery to replace a heart valve.
It's widely known that warfarin sensitivity varies. It can take weeks or even months of repeated blood tests and dose adjustments to determine the right dose for each patient.
Often times patients during this trial and error phase of dose adjustment patients are at an extremely high risk for either unwanted blood clotting (thromboembolism) from too little warfarin, or dangerous bleeding from too much warfarin.
Epstein's study is said to be the first national, prospective, comparative effectiveness study to evaluate the role of genetic testing in assisting physicians to gauge the best warfarin dose and monitoring intensity during the early dose-adjustment phase of treatment.
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