Platelet Function Testing for Cardiac Surgery Patients on Antiplatelet Therapy: The Extreme Variability of Point-Of-Care Tests

Abstract

Platelets play a pivotal role in coagulation, and both quantitative and qualitative platelet defects can lead to major bleeding during and after surgery. Moreover, patients with cardiac disease are often on antiplatelet therapies as part of routine management, which predisposes to increased risk of perioperative bleeding due to inhibited platelet function. In some cases, antiplatelet therapy is interrupted briefly before scheduled cardiac surgery in order to reduce the risk of haemorrhage; however, this can increase the risk of perioperative thrombosis if not monitored carefully. Furthermore, individual patients respond differently to antiplatelet therapy. Therefore, point-of-care tests that determine platelet function could provide improved, personalised evidence-based treatment and management of such high-risk cardiac patients. This article reviewed various methods and devices used for testing platelet function at point-of-care in cardiac patients on antiplatelet therapy who were undergoing cardiac surgery. The consensus is that point-of-care testing of platelet function can offer three main advantages for the timely management of preoperative and perioperative coagulation in cardiac surgery patients who are on antiplatelet therapy: 1.) Assessing the effectiveness of antiplatelet therapy to quickly identify patients with resistance, who have increased risk of pre- and perioperative thrombotic events. 2.) Assessing platelet function recovery following treatment withdrawal to determine optimal timings for cardiac surgery, in order to avoid excessive haemorrhage, and reduce waiting times and hospitalisation costs for patients scheduled for cardiac surgery. 3.) Efficient use of transfusion blood products. However, an important finding of this review is that there exists extreme variability and a lack of correlation among the various point-of-care platelet function testing assays. Furthermore, the assays show inconsistencies in predicting blood loss, or adverse thrombotic and haemorrhagic events in cardiac patients on antiplatelet therapy and those undergoing surgery. It is imperative that point-of-care platelet function tests accurately predict the risks of bleeding and thrombosis in order to be clinically relevant in the preoperative, perioperative and long-term post-operative care and management of cardiac surgery patients on antiplatelet therapy. The extreme variability of these tests, coupled with inconsistencies in predicting adverse events do not support the high costs of large-scale implementation.