Summary and Concluding Remarks
Platelet reactivity testing using VerifyNow has an important role in monitoring the therapeutic efficiency of clopigogrel and the safety of therapeutic escalation to more potent drugs that confer an increased bleeding risk. It has found to be predictive of clinical outcomes in numerous cardiovascular and neurovascular interventions where antiplatelet therapies are employed. However, further study is needed to fully assess its prognostic role. While the prognostic value of testing in PCI has been demonstrated repeatedly in cohort studies and meta-analyses, randomised controlled studies investigating the clinical utility of the technique to guide treatment decision have had mixed results. Reasons may include a lack of consensus on the optimal method to quantify high on-treatment platelet reactivity and the cut-off value associated with clinical risk. At present, it seems reasonable to assess platelet function in high-risk patient groups. A combination of platelet tests may be useful to further define a high-risk population, together with the assessment of demographic and genetic factors associated with high risk. Point-of-care genetic testing may also be combined with platelet reactivity testing. Clinical trials using a combined genotyping and phenotyping approach are underway to better define the role of such tests in guiding antiplatelet therapy in clinical practice.
The advent of the stronger P2Y12 inhibitors such as prasugrel and ticagrelor and their increased cost and bleeding risk compared with clopidogrel, will necessitate the establishment of a therapeutic window to achieve optimal and cost-effective platelet inhibition while minimising bleeding risk.2,3 As we move towards conclusively defining a therapeutic window for antiplatelet agents, platelet reactivity testing will become a central tool in the practice of personalised antiplatelet strategies.