Tests to Measure Safety of Anti-Clotting Drugs of Limited Value

Can't predict which patients are at risk for excessive bleeding during surgery, study finds

By Ed Edelson
HealthDay Reporter

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TUESDAY, Feb. 23 (HealthDay News) -- Tests that try to single out who will have bleeding problems when they get a clot-preventing drug such as Plavix before surgery aren't ready for regular use, a new Dutch study concludes.

Three of the six tests, which measure the function of platelets, the blood cells that clump together to form clots, did provide some useful information, according to the report in the Feb. 24 issue of the Journal of the American Medical Association.

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"However, the predictability of these three tests was only modest," the report added. "None of the tests provided accurate prognostic information to identify patients at higher risk of bleeding."

And so, the study "does not support the use of platelet function testing to guide clinical practice in a low-risk population of patients," the Dutch researchers wrote.

The conclusion did not surprise U.S. doctors who have studied the issue. "For my purposes, these tests are research tools," said Dr. Deepak Bhatt, chief of cardiology at the VA Boston Healthcare System, and a member of a group of U.S. cardiologists who said pretty much the same thing in a 2008 statement.

Yet, the Dutch study "is well-done and a valuable contribution to the field," Bhatt said. "It shows just how much different tests add to clinical judgment."

The study included 1,069 people given clopidogrel (Plavix) before having stents implanted after artery-opening angioplasty. They were followed for a year to record the incidence of death, nonfatal heart attacks or strokes, and new blockages of the treated arteries. Three of the tests had some predictive value for those events, but three didn't. None predicted the major side effect of Plavix treatment, which is excessive bleeding.

The study is a starting point for understanding a complex clinical situation, Bhatt said. "It sets us up for the next step. You have a patient at moderate risk; what do you do with that test information? That is a question that needs to be answered."

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