Novel Uses for Platelet Function Testing in the Clinical Laboratory: Where Are We Now?

Abstract

Platelet function testing (PFT),7 usually performed by techniques such as light transmission aggregometry (LTA), has traditionally been used to diagnose inherited qualitative and quantitative defects in platelet function, such as von Willebrand disease or Glanzmann thrombasthenia. With the increased use of antiplatelet agents to prevent arterial thrombosis and the interest in identifying patients at risk for thrombosis despite antiplatelet therapy, the use of PFT to monitor the response to and/or titrate antiplatelet therapy (primarily aspirin and clopidogrel) has become a hot topic. Investigators and practitioners in surgery, critical care, and trauma have also pursued other nonstandard tests of coagulation, such as viscoelastic coagulation testing, to allow more-robust prediction of patients at risk for massive bleeding during invasive procedures or after major trauma. There is considerable controversy regarding the use of PFT and viscoelastic coagulation tests to monitor response to antiplatelet therapy or to guide transfusion decisions for critically ill patients. In this Q&A article, 4 experts in platelet function give their views on both the evidence and current best practice for application of PFT in these nontraditional settings. What PFTs are used clinically in your institution? What population of patients is being tested, and what clinical decisions are made based on the results? Gilles Montalescot: We perform VerifyNow (Accumetrics), light-transmission and whole-blood impedance aggregometry and perform some flow cytometric evaluation of platelet reactivity in our research unit for clinical research only; we do not routinely test patients in the catheritization laboratory. Rarely, however, we perform testing on patients when there is a good reason to do so, e.g., assessing compliance with treatment, stent thrombosis, very high–risk patients—all of which are situations that were not evaluated in the ARCTIC (Double Randomization of a Monitoring Adjusted Antiplatelet Treatment versus a Common Antiplatelet Treatment for DES Implantation, and Interruption versus Continuation of …