From the Guidelines
Platelet function assays should be reserved for patients with a history of bleeding disorders, those on antiplatelet medications, or individuals with clinical suspicion of platelet dysfunction, as they have limited utility in routine preoperative assessment of bleeding risk. The role of platelet function assay in preoperative assessment of bleeding risk is to help determine residual platelet inhibition before surgery, particularly in patients on antiplatelet therapy such as aspirin or P2Y12 inhibitors (clopidogrel, ticagrelor, prasugrel) 1. Common platelet function tests include light transmission aggregometry, PFA-100/200, and point-of-care tests like VerifyNow.
The recommended timing for discontinuation of antiplatelet therapy varies by medication: aspirin may be continued for many surgeries except neurosurgery and some ophthalmologic procedures, while P2Y12 inhibitors typically require 5-7 days of discontinuation 1. However, platelet function assays have significant limitations, including poor standardization across laboratories, variable correlation with clinical bleeding, and inability to predict surgical bleeding in patients without known platelet disorders 1.
Some studies suggest that platelet function testing could be a better means to predict perioperative-bleeding risk than duration of APA discontinuation, particularly in patients undergoing coronary bypass surgery 1. For example, a study using TEG1 Platelet Mapping reported that being in the upper tertile of platelet dysfunction measured with this test predicted transfusion requirements after coronary artery bypass surgery in a cohort of 99 patients 1. Another study with 180 patients reported that platelet function testing with the same test was associated with a mean discontinuation duration inferior to 50% compared with five-day discontinuation, without increased bleeding risk 1.
Clinical assessment, including a thorough bleeding history, remains the cornerstone of preoperative bleeding risk evaluation, with platelet function testing serving as an adjunct tool in specific clinical scenarios rather than a universal screening method 1. In agreement with the European Society of Anaesthesiology, it is suggested that platelet function testing be performed preoperatively in order to identify a platelet dysfunction whatever the causes, APA and others, when it is suspected on a clinical basis, in teams trained in and accustomed to the use of the tests 1.
Key points to consider when using platelet function assays in preoperative assessment of bleeding risk include:
- The test should be used in patients with a history of bleeding disorders, those on antiplatelet medications, or individuals with clinical suspicion of platelet dysfunction
- The test should be used to determine residual platelet inhibition before surgery, particularly in patients on antiplatelet therapy
- The recommended timing for discontinuation of antiplatelet therapy varies by medication
- Platelet function assays have significant limitations, including poor standardization across laboratories and variable correlation with clinical bleeding.
From the Research
Platelet Function Assay in Preoperative Assessment
The role of platelet function assay in preoperative assessment of bleeding risk is a significant area of research, with several studies investigating its potential benefits.
- Platelet function is affected by multiple factors, including patient and procedural characteristics, and point-of-care (POC) multiple electrode aggregometry (MEA) can rapidly detect and quantify platelet dysfunction 2.
- The predictive value of platelet function point-of-care tests for postoperative blood loss and transfusion in routine cardiac surgery has been systematically reviewed, highlighting the uncertainty of the association between platelet function measured by ex vivo assay and the occurrence of bleeding events 3.
Association with Postoperative Bleeding
Studies have shown that reduced ADP-induced platelet aggregation at baseline is associated with increased postoperative blood loss in high-risk cardiac surgery patients 2.
- A linear relationship was present between ADP-induced platelet aggregometry at baseline and postoperative blood loss, and in aspirin users, the maximum decline in platelet function between baseline and CPB decannulation was related to postoperative blood loss 2.
- Preoperative platelet function testing was the most significant predictor of excessive bleeding, need for blood and platelet transfusion in patients on anti-platelet therapy until the time of surgery 4.
Clinical Applications
The use of platelet function assays in clinical practice has been explored, with some studies suggesting that preoperative assessment with ISTH-BAT and laboratory tests may not be useful in identifying mild previously undiagnosed bleeding disorders or predicting bleeding complications in selected patients undergoing elective surgery 5.
- However, other studies have demonstrated that an objective measurement of platelet function among patients undergoing cardiac surgery during antiplatelet therapy may reduce the waiting period while mitigating the risk of bleeding 6.
- Available platelet function assays can assess pharmacodynamic effects, and the association between platelet inhibition and other clinical factors with surgery-related bleeding has been investigated 6.
Key Findings
Key findings from the studies include:
- Reduced ADP-induced platelet aggregation at baseline is associated with increased postoperative blood loss in high-risk cardiac surgery patients 2.
- Preoperative platelet function testing is a significant predictor of excessive bleeding, need for blood and platelet transfusion in patients on anti-platelet therapy until the time of surgery 4.
- Platelet function assays may have a role in reducing the waiting period while mitigating the risk of bleeding in patients undergoing cardiac surgery during antiplatelet therapy 6.