Pharmacogenomic Warfarin Dosing: Worth the Cost?

Mark J. Alberts, MD


December 23, 2013

Similar Results, Separately and Combined

What did they find? Either separately or combined, the 3 studies found no difference in clinical events, such as ischemic or hemorrhagic events, in patients who received warfarin doses based on the results of genetic testing vs a routine clinical algorithm.

Two of the 3 studies found no difference in the time span during which patients were within the therapeutic range with genetic dosing vs routine clinical dosing. Only 1 of the 3 studies found a statistically significant difference in terms of time within the therapeutic range using genetic testing vs a routine algorithm.

There may be many potential flaws in the studies in terms of differences in the patient population -- perhaps the dosing algorithms between genetic and nongenetic testing were not optimally tuned or paired up -- and a host of other factors. But at the end of the day, after testing more than 2000 patients in these fairly large studies, I believe I can say that there is no compelling evidence to routinely perform genetic testing when we are trying to calculate warfarin dosage.

The studies did find some racial differences, particularly among black patients, with genetic testing vs nongenetic testing. But this was a subgroup-of-a-subgroup type of phenomenon.

Having point-of-care testing that could accurately predict which dose of warfarin we should use would be wonderful. But we are not there yet. Even with point-of-care testing, it does not seem that the differentiation of dosing combined with a host of other environmental and medical factors are really refined enough to say clearly and unambiguously that genetic testing gives us an answer, in enough patients enough of the time, that they can be on autopilot in terms of dosing and testing.

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