Correlation of high post-treatment platelet reactivity assessed by light transmittance aggregometry and the VerifyNow P2Y₁₂ assay

In vitro “high post-treatment platelet reactivity” (HPPR) measured with light transmittance aggregometry (LTA) and the VerifyNow P2Y₁₂ assay has been associated with an increased risk of ischemic events after percutaneous coronary intervention (PCI). However, there are many criteria for HPPR according to the methods used for assessment, and correlations among suggested criteria have not been evaluated. To this end, we enrolled 1,058 unselected patients undergoing PCI in real clinical practice, simultaneously assessed platelet measures with LTA (both 5 and 20 μmol/l ADP-induced) and the VerifyNow P2Y₁₂ assay, and based on previous studies, evaluated the following criteria for HPPR: 5 or 20 μmol/l ADP-induced maximal platelet reactivity (PR_max) ≥50%; 5 μmol/l ADP-induced late PR (PR_late) >14%; 20 μmol/l ADP-induced PR_max ≥62%; and P2Y₁₂ reaction unit (PRU) ≥240. Receiver-operating characteristics (ROC) curve analysis demonstrated that PRU (cut-off = 241) distinguished between patients with and without 5 μmol/l ADP-induced PR_max ≥50% (area under curve [AUC] 0.822, sensitivity 83.0%, specificity 66.0%, P < 0.001), and 20 μmol/l ADP-induced PR_max ≥62% (AUC 0.840, sensitivity 80.7%, specificity 71.4%, P < 0.001), respectively. PRU ≥240 showed a moderate agreement with 5 μmol/l ADP-induced PR_max ≥50% (κ = 0.438, concordant rate 71.6%, P < 0.001) and 20 μmol/l ADP-induced PR_max ≥62% (κ = 0.505, concordant rate 75.1%, P < 0.001). Cut-offs matched for 20 μmol/l ADP-induced PR_max ≥50% (PRU = 195) and 5 μmol/l ADP-induced PR_late >14 (PRU = 194) also were similar. The presence of significant correlations between the suggested criteria for HPPR has practical implications on the possible use of the VerifyNow P2Y₁₂ assay for risk stratification in PCI-treated patients.