Platelet to red cell distribution width ratio for predicting clopidogrel efficacy in patients undergoing percutaneous coronary interventions: insights from ONSIDE-TEST study.

INTRODUCTION Dual antiplatelet therapy (DAPT) with aspirin and clopidogrel remains a cornerstone of pharmacotherapy after percutaneous coronary intervention (PCI). It has been demonstrated that even up to 30% of patients receiving DAPT is characterized by inadequate response to clopidogrel, namely high on-treatment platelet reactivity (HPR). The platelet to red cell distribution width (P-RDW) ratio represents an indicator of cardiovascular risk and may be related to HPR. OBJECTIVES The aim of the present study was to establish whether the P-RDW ratio predicts HPR in clopidogrel-treated patients undergoing elective PCI. PATIENTS AND METHODS This is a subanalysis of the prospective, randomized controlled ONSIDE TEST Study (NCT01930773). A total of 70 patients were included in the present investigation. Of them 12 were identified with inadequate response to clopidogrel (HPR). The HPR was defined as the values above the threshold of 208 platelet reactivity units (PRU>208) by aggregometry VerifyNow P2Y12. RESULTS The mean P-RDW  ratio (SD) was lower in patients with HPR, as compared to non-HPR patients  (14.37(4.13) vs. 17.734(4.96), p = 0.03). Logistic regression analysis showed that P-RDW ratio was significantly related to HPR (p=0.03). Using a cut-off level of 15.23, P-RDW ratio predicted HPR with sensitivity of 69 % and specificity of 75 % (Odds ratio: 6.67, 95% confidence interval: 0.561-0.890, p = 0.02; receiver operating characteristic curve: 0.723). CONCLUSIONS P-RDW ratio may serve as supplementary tool for identification of patients at risk of HPR. Further studies are warranted to assess its role in planning the DAPT among patients undergoing PCI.