Distribution of VerifyNow Aspirin and P2Y12 Reaction Units in Adults Undergoing Preoperative Evaluation: A Single-Institution Retrospective Study

Background: VerifyNow Aspirin and P2Y12 assays (Werfen, Spain) measure residual platelet reactivity and may complement preoperative bleeding-risk assessment, but baseline values of aspirin reaction units (ARU) and P2Y12 reaction units (PRU) in individuals without antiplatelet exposure remain poorly characterized.We analyzed the distributions of ARU and PRU values in Korean adults undergoing preoperative evaluation.Methods: Adults aged ≥ 20 years who underwent outpatient preoperative VerifyNow testing from September 2021 through November 2024 were retrospectively reviewed.Patients with records of prescriptions for any antiplatelet or anticoagulant agents during the preceding 3 years were excluded.ARU and PRU distributions were analyzed by age and sex, along with their associations with hematocrit (Hct) and platelet count.Results: Of 14,369 patients (36.3% male; median age, 49 years), 14,351 and 10,487 had ARU and PRU results, respectively.Median ARU was 629 (interquartile range, 601-645) and median PRU was 239 (205-269).ARU <550 occurred in 11.9% (1,703/14,351) of patients and was more frequent among those aged ≥50 than among those aged <50 years (16.9% vs. 6.9%;OR, 2.72; 95% CI, 2.44-3.03;P <0.001).Median PRU was higher in women than in men overall (252 vs. 195) and across all age groups (all P <0.001).Hct was inversely correlated with PRU (ρ=-0.731).In mutually adjusted models, PRU decreased by 6.71 per 1-percentage-point increase in Hct and was 18.60 units lower in men (adjusted R²=0.553), whereas the ARU model explained 6.0% of the variance.Conclusions: In this first large-scale analysis, preoperative ARU and PRU distributions in Korean adults were comparable to previously reported values.PRU was strongly associated with Hct and sex, suggesting that these factors should be considered when interpreting PRU values.