Measuring high on-treatment platelet reactivity in clinical practice; should we use a panel of platelet function...

: High on-treatment platelet reactivity (HPR) on P2Y12-inhibitors in patients treated with dual antiplatelet therapy is strongly associated with adverse ischaemic events. Studies have shown conflicting results with regard to the correlation and agreement between the different tests. Several assays are available to establish HPR. A composite advice based on more than one test might be a better way to identify HPR patients. To compare HPR rates and agreement between individual platelet function tests and a panel of three tests In our large percutaneous coronary intervention centre, all patients who suffered a stent thrombosis were invited back to a dedicated clinic. Platelet function testing was performed in all patients and matched control patients. HPR rates were compared between individual tests and with a composite comprised of three tests. A total of 242 patients were included, of whom in 193 patients all tests were available. HPR rates ranged from 14.6% [VerifyNow cut-off >235 platelet reactivity units (PRU)] to 49.7% (Vasodilator-Stimulated Phosphoprotein Assay). HPR according to the composite advice (≥2 out of 3 tests indicating HPR) was present in 29.8% of patients. The best correlation with the composite advice was observed with light transmittance aggregometry (kappa = 0.78) and VerifyNow (lower cut-off >208 PRU; kappa = 0.68). VerifyNow with cut-off more than 235 PRU identified the smallest proportion of patients with HPR, whereas Vasodilator-Stimulated Phosphoprotein Assay seemed to 'over-identify' HPR. In this real life patient cohort, a large variability was observed between four different platelet function tests. The use of a composite advice based on three tests is a promising alternative.