Platelet function tests and flow cytometry to monitor antiplatelet therapy.

There are numerous methods to measure platelet function in specialized laboratories. They provide valuable results for research or small patient studies, but none of these tests is currently used to guide antiplatelet therapy in routine clinical practice. Aggregometry is the most commonly used test, but this technique is time-consuming and pre-analytical preparation, choice of anticoagulant, and agonist have not been standardized. The Rapid-Platelet-Function-Analyzer uses whole blood to measure glycoprotein (GP) IIb/III inhibitor activity. This test is quick and simple and results for abciximab correlate closely with aggregometry. The platelet function analyzer PFA-100 is a good screening method to detect platelet function defects. The closure time of the PFA is also sensitive for aspirin-resistance that affects many patients. Flow cytometry can monitor a whole panel of platelet activation markers and platelet interactions with other cells. It can quantitate receptor expression and inhibition. Although cytometry is time-consuming and expensive, it is a valuable tool for research. Platelets have many different functions. This requires specific tests optimized for each of the different functions. Each test has advantages and disadvantages and should be interpreted only in concert with a thorough history and physical examination. The ideal test should be simple, quick, inexpensive, and available on a 24-hour basis.