Assessment of platelet function: Laboratory and point-of-care methods

Abstract

In the event of blood vessel damage, human platelets are promptly recruited on the site of injury and, after their adhesion, activation and aggregation, prevent blood loss with the formation of a clot. The consequence of abnormal regulation can be either hemorrhage or the development of thrombosis. Qualitative and/or quantitative defects in platelets promote bleeding, whereas the residual reactivity of platelets, despite antiplatelet therapies, play an important role in promoting arterial thrombotic complications. Platelet function is traditionally assessed to investigate the origin of a bleeding syndrome, to predict the risk of bleeding prior surgery or during pregnancy or to monitor the efficacy of antiplatelet therapy in thrombotic syndromes that, now, can be considered a new discipline. "Old" platelet function laboratory tests such as the evaluation of bleeding time and the platelet aggregation analysis in platelet-rich plasma are traditionally utilized to aid in the diagnosis and management of patients with platelet and hemostatic disorders and used as diagnostic tools both in bleeding and thrombotic diathesis in specialized laboratories. Now, new and renewed automated systems have been introduced to provide a simple, rapid assessment of platelet function including point of care methods. These new methodologies are also suitable for being used in non-specialized laboratories and in critical area for assessing platelet function in whole blood without the requirement of sample processing. Some of these methods are also beginning to be incorporated into routine clinical use and can be utilized as not only as first panel for the diagnosis of platelet dysfunction, but also for monitoring anti-platelet therapy and to potentially assess risk of both bleeding and/or thrombosis.© 2014 Baishideng Publishing Group Inc. All rights reserved.Key words: Platelets; Method; Test; Point of care testing; Laboratory assessment; Bleeding; Thrombosis; Platelet function Core tip: This review discussed the scenario of available platelet function laboratory and point-of-care methods suitable in different clinical setting. As this matter has become of crucial importance in the bleeding management and for monitoring antiplatelet therapies, improved ability to assess platelet function in a timely and efficient manner is essential. Traditional platelet function methods, requiring a fair degree of expertise, have been limited to specialized laboratory. Many efforts have been carried out for improving platelet function assays for centralized laboratory, such as different point-of-care testing methodologies have been developed. Moreover, different guidelines and recommendations for their method standardization are growing.

Anti-platelet Therapy Resistance – Concept, Mechanisms and Platelet Function Tests in Intensive Care Facilities

“…LTA is performed on platelet rich plasma and measures changes that occur in light transmittance after platelet-platelet aggregation as a response to the addition of several agonists (ADP, arachidonic acid, collagen, epinephrine, ristocetin, thrombin receptor activating peptide etc) [26,73]. It can be used to monitor therapy with aspirin, thienopyridines and GPIIb/ IIIa inhibitors.…”

“…Impedance aggregometry is based on the principle that activated platelets display their surface receptors which allow them to attach to artificial surfaces [73]. This test measures the change in impedance between two electrodes within a whole blood sample.…”

“…Using appropriate cartridges, platelet function analyser simulates primary haemostasis. Citrated whole blood is passed under high shear stress through a microscopic aperture coated with collagen and an agonist, ADP or epinephrine [73]. As the blood passes through the system, platelets undergo adhesion and aggregation, a platelet clot forms and gradually occludes the opening.…”

“…GPIIb/IIIa assay that uses iso-thrombin-receptor activating peptide as agonist and is sensitive to GPIIb/ IIIa inhibitors; (2) P2Y12 assay, sensitive to thienopyridines, with ADP as the agonist in the presence of prostaglandin E1 which abolishes signalling through P2Y1 receptors; and (3) Aspirin assay, i.e. sensitive to aspirin, with arachidonic acid asthe antagonist [73]. Given the fact that the system is based on the same concept as LTA, these two correlate well [81].…”

“…Light Transmission Aggregometryor low shear aggregometry, is a method developed in the 1960s, and is regarded as the gold standard test for assessing platelet function and is still utilised to validate newer tests [26,73]. LTA is performed on platelet rich plasma and measures changes that occur in light transmittance after platelet-platelet aggregation as a response to the addition of several agonists (ADP, arachidonic acid, collagen, epinephrine, ristocetin, thrombin receptor activating peptide etc) [26,73].…”