Following activation and aggregation, human platelets play an important role in promoting vascular and stent thrombosis. By inhibiting platelets, aspirin and clopidogrel limit this process; used in combination they are particularly helpful when administered to patients with acute coronary syndromes undergoing percutaneous coronary intervention with stenting. Platelet function is traditionally assessed by light transmission aggregation (LTA) test in platelet-rich plasma (PRP). By using different agonists to induce aggregation, the extent of platelet inhibition can be monitored. As platelet LTA presents some drawbacks (manual sample preparation, selection of agonists and their concentration, time-consuming), new and renewed automated systems have been introduced to provide a simple, rapid assessment of platelet function, including point-of-care (POC) methods that are also suitable for use in non-specialized laboratories.
Platelet function, aggregation, point-of-care testing, platelet reactivity, coronary artery disease, antiplatelet therapy
The author has no conflicts of interest to declare.
November 06, 2008 |
January 09, 2009 |
US Cardiology, 2009;6(1):75-80
Rita Paniccia, PhD, Thrombosis Center, University of Florence, Azienda Ospedaliero-Universitaria Careggi, Viale Morgagni, 85 50134 Florence, Italy. E: firstname.lastname@example.org
The goal of platelet function tests used in cardiac catheterization laboratories and intensive cardiac units is to guide antiplatelet therapy to the optimal dose for the prevention or treatment of thrombosis, minimizing hemorrhagic side effects in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI).1–4 Platelet function tests measure the platelet capacity to adhere (bleeding time [BT]) and aggregate to each other (platelet light transmission aggregation [LTA]) in response to external aggregating agents, i.e. adenosine diphosphate (ADP), arachidonic acid (AA), collagen, epinephrine (EPI), and others.5,6 These methods are usually performed in specialized hemostasis laboratories, often in close proximity to associated clinics.
Historically, these methods represented a challenge for clinical laboratories due to the lack of reliable, accurate, and easy-to-perform test procedures. Drawbacks of platelet function tests are mostly due to the fact that platelets are prone to the activation of artifacts during the drawing of blood. In addition, BT and LTA may be time-consuming and cumbersome or prone to operator-specific variables. These drawbacks have limited their widespread clinical use. Since the evaluation of platelet function has become of crucial importance in the management of ACS patients on antiplatelet therapy, improved ability to assess platelet function in a timely and efficient manner is essential. As a result, simpler platelet function tests that may be utilized as point-of-care (POC) tests, or at least within non-specialized laboratories, have been proposed (see Table 1).1,2,5,6
This article tries to offer a simple updated summary of available platelet function tests more suitable for the cardiovascular clinical setting to monitor residual platelet reactivity (RPR) in ACS patients on antiplatelet therapy.
Conventional Platelet Function Tests
BT, the oldest test for measuring platelet function, evaluates the capacity of platelets to form a hemostatic plug. The test measures the time that the platelets employ to occlude a standardized in vivo skin wound by evaluating the ability of platelets to stop the bleeding.7 It is useful as a screening test to identify either congenital or acquired platelet disorders.