PO035 | ASSESSMENT OF HIGH-ON-TREATMENT PLATELET REACTIVITY IN PATIENTS ON DUAL ANTIPLATELET THERAPY USING THE FULLY AUTOMATED COAGULATION ANALYZER SYSMEX CN-6500: A COMPARATIVE STUDY WITH THREE POINT-OF-CARE TESTS

E. Falcinelli¹, L. Bury¹, E. Giglio¹, A.M. Mezzasoma¹, V. Fazzi¹, M. del Pinto², M. Lenti³, A. Rechner², P. Gresele¹ | ¹Dept of Medicine and Surgery, Section of Internal and Cardiovascular Medicine; ²Dept. of Cardiology; ³Dept of Vascular Surgery, University of Perugia, Italy; ⁴Sysmex Europe

Background and aims. High-on-treatment platelet reactivity (HTPR) in patients on dual antiplatelet therapy (DAPT) with P2Y12-receptor antagonists and aspirin for an acute coronary syndrome (ACS) or a recent carotid artery stent (CAS) has been associated with enhanced adverse cardiovascular events. Platelet function testing may thus be important to monitor antiplatelet therapy in patients at high cardiovascular risk, however different sensitivity across testing methods remains a challenge. Recently, automated light transmission aggregometry (LTA) on a coagulation analyzer (CN-6500 Sysmex) has been developed together with a new aggregation readout (PAL: platelet aggregation level) to assess HTPR in patients on DAPT. Aim of the study was to evaluate residual platelet reactivity in patients on DAPT with aspirin plus P2Y12 inhibitors (e.g., clopidogrel, ticagrelor, prasugrel) comparing the Sysmex CN-6500 with three established point of care (POC) instruments: the PFA-100®, the Multiplate® and the VerifyNowTM.
Methods. Patients with recent ACS or CAS on DAPT were enrolled. The PAL score was calculated by Sysmex CN-6500 on the aggregation waves obtained with ADP 1 and 10 μM (APAL) and compared with the VerifyNow P2Y12 test (PRU), Multiplate using ADP as agonist (U) and PFA-100® using the INNOVANCE® P2Y cartridge. HPTR was defined by results above/below the respective validated cut-off values.
Results. 100 patients (29 females), median age 67 years (95%CI 58-76) on DAPT with ASA 100 mg + Clopidogrel (n=52), Ticagrelor (n=44) or Prasugrel (n=4) were studied. Median platelet count was 198 (95%CI 169-247) × 103/L. A significant correlation was found between the APAL score and the results obtained with the other tests, with higher correlation coefficients for Multiplate-ADP (r= 0.61, p< 0.001) and VerifyNow PRU (r= 0.59, p< 0.001) compared with PFA-100® P2Y (r= −0.57, p< 0.001). In the overall population the prevalence of HTPR varied from 7% to 13%: it was 13% when measured by APAL, 9% by Innovance P2Y-PFA®, 8% by Multiplate-ADP and 7% by the VerifyNow P2Y12 assay, with no statistically significant differences among the assays (Figure 1). DAPT with Ticagrelor was associated with significantly lower rates of HTPR compared to clopidogrel, with HTPR prevalence of 7%-23% for clopidogrel versus 0%-2.2% for ticagrelor. None of the patients treated with prasugrel exhibited HTPR.
Conclusions. The CN-6500 automated coagulation analyzer is a useful tool for detecting HTPR reactivity in patients on DAPT. PAL scores showed good agreement with established POC assays and reliably reflected antiplatelet drug effects. Our study also confirms significant differences in sensitivity to HTPR among different platelet function tests, and their clinical relevance warrants further investigation.