Platelet function testing

To measure platelet reactivity, the VerifyNow P2Y12 assay was performed in accordance with the manufacturer’s instructions. The VerifyNow P2Y12 assay is a point-of-care turbidimetry-based optical detection that estimates the inhibition of P2Y12 receptors by their antagonists by assessing the level of P2Y12 receptor activation. ADP simultaneously activates P2Y1 and P2Y12 receptors, thus the disposable assay device contains 20 µM ADP to induce platelet aggregation and 22 nM PGE1 to reduce P2Y1 activation by ADP. The assay reports values in P2Y12 reaction units (PRU) with a proprietary algorithm. In this study, HPR was defined as ≥300 PRU and LPR as <170 PRU in order to maximally discriminate between the patients in the 2 groups.

Since the VerifyNow P2Y12 assay was a whole blood assay which was unable to evaluate platelet reactivity in platelet-rich plasma, after treatment of ABT-737, platelet reactivity was assessed using light transmittance aggregometry (LTA) assay. To induce platelet aggregation, platelet-rich plasma was stimulated with 20 µM ADP and 22 nm PGE1 in accordance with the reagents within VerifyNow P2Y12 assay devices. Platelet aggregation was measured by a 4-channel LBY-NJ4 light transmittance aggregometer (Precil, Beijing, China) and expressed as the maximum percent change in light transmittance from platelet-poor plasma which was set as a reference.