021: Clopidogrel low response and correlation between the different tests: light transmission aggregometry, VerifyNow-P2Y12 and V ASP

Abstract

BackgroundClopidogrel low response correlates with poor prognosis after percutaneous coronary intervention (PCI). Many biological tests are currently available to test the clopidogrel response. However, the presence of any correlation between the different tests is today poorly reported.MethodsIn this prospective study, clopidogrel response was assessed in 100 consecutive patients. All patients were tested between 18h and 24h after a600mg clopidogrel loading dose using 3 different tests: light transmission aggregometry with 10μmol ADP (LTA, results expressed as platelet inhibition percentage), VerifyNow-P2Y12 (VN, results expressed as PRU) and vasodilatator stimulated phosphoprotein (VASP, results expressed as IRP). Patients under chronic clopidogrel therapy were excluded.ResultsThe mean platelet inhibition percentage, PRU value and IRP value were 38.5±13% by LTA, 178±89 PRU by VN and 52±21% by VASP. When results were analyzed as continuous variables, there was a good correlation between the different tests: LTA/VN (R2=0,642, p<0,001), LTA/VASP (R2=0,409, p<0,001) and VN/VASP (R2=0,616, p<0,001). However, when results were analyzed as pre-specified cut-off points to define patients as “low or good responders” (according to the literature: 50% for LTA, 235 PRU for VN and 50% IRP for VASP), only 47% of the patients were defined as “good” or “low responders” by the 3 tests. Altogether, 33% of the patients were defined as “low responders” by only 1 test, 20% by 2 tests and only 16% by the 3 tests.ConclusionIf the correlation between the different tests is good when results are analyzed as continuous variables, each individual is rarely (less than 50%) defined as “low or good responder” by all the 3 tests when recognized cut-off values are used. In that way, a sole test might not be sufficient to manage antiplatelet therapy in an individual patient