(Ivanhoe Newswire) -- An analysis of six tests used to measure platelet
function and gauge the effectiveness of anti-platelet drugs for patients
undergoing a cardiac procedure such as a coronary stent implantation found that
only three of the tests were associated with a modest ability to predict
outcomes such as heart attack or death.
Dual anti-platelet therapy with aspirin and clopidogrel, an anti-platelet agent
used to inhibit blood clots, reduced vascular obstruction complications in
patients undergoing percutaneous coronary intervention (PCI), procedures such as
balloon angioplasty or stent placement used to open narrowed coronary arteries,
with stenting. However, the individual response to dual anti-platelet therapy is
not uniform.
Nicoline J. Breet, M.D., and colleagues, of St. Antonius Hospital in Nieuwegein,
the Netherlands, evaluated the ability of multiple platelet function tests to
predict atherothrombotic events, including stent thrombosis (blood clot within
the stent) in 1,069 clopidogrel-pretreated patients undergoing elective coronary
stent implantation. Using blood samples, platelet reactivity was measured in
parallel with six platelet function tests. The primary outcome measured was a
composite of all-cause death, nonfatal heart attack, stent thrombosis and
ischemic stroke.
The researchers found that at one-year follow-up, the primary outcome occurred
more frequently in patients with high platelet reactivity when assessed by three
of the tests -- light transmittance aggregometry, VerifyNow and Plateletworks,
which also had modest ability to discriminate between patients having and not
having a primary event. The three other testing methods -- IMPACT-R, Dade PFA
collagen/ADP, and Innovance PFA P2Y -- were unable to discriminate between
patients with and without the primary outcome. None of the tests identified
patients at risk for bleeding.
"In conclusion, of the platelet function tests assessed, only light
transmittance aggregometry, VerifyNow, and Plateletworks were significantly
associated with the primary end point,” study authors wrote. “However, the
predictability of these three tests was only modest. None of the tests provided
accurate prognostic information to identify patients at higher risk of bleeding.
Thus, [this study] does not support the use of platelet function testing to
guide clinical practice in a low-risk population of patients undergoing elective
PCI."
SOURCE: Journal of the American Medical Association (JAMA), February 24, 2010
