A-173 Evaluation of Plateletworks and TEG 6S Platelet Mapping: Performance Characteristics and Differentiation of Healthy Donors from Patients on Dual Antiplatelet Therapy

Abstract Background Platelet function tests (PFT) help assess bleeding risk and guide appropriate hemostatic measures in patients on antiplatelet therapy undergoing emergent surgical interventions. Light transmission aggregometry (LTA, BioData Corporation), the gold standard for assessing platelet function, cannot be performed rapidly enough for emergent interventions. In this study, we compared two PFT, Plateletworks (Helena Laboratories) and TEG 6S (TEG, Haemonetics) adenosine diphosphate-(ADP) and arachidonic acid (AA)-induced platelet function, evaluating analytical imprecision and their ability to differentiate healthy controls from patients with acute coronary syndrome (ACS) on dual antiplatelet therapy. Methods Fresh specimens were collected from healthy donors (HD, N=19) and a patient group (PG, N=17) on both aspirin and clopidogrel taken within 24 hours of procedure. Percent aggregation was measured according to manufacturers’ instructions using Plateletworks and TEG, utilizing both AA and ADP and compared to LTA performed on a PAP-8E Platelet Aggregometer. Two separate venipuncture collections from HD were used to obtain repeat measures of Plateletworks and TEG to assess variability in platelet function due to pre-analytical variables. Using a two-way nested ANOVA model on data from HD, we estimated variability between replicates of a single sample (intra-assay imprecision) and between blood draws within a single patient (inter-assay imprecision), reported as coefficient of variation (CV%). Platelet function results were summarized as median (interquartile range [IQR; 25th-75th percentiles]) and compared between groups using nonparametric Wilcoxon rank-sum test. Receiver operating characteristic (ROC) analysis (using duplicate means from first blood draw) was performed. Results Plateletworks AA % aggregation, medians (IQR) were 96.3 (95.3-97.1) for HD and 48.9 (46.8-54.8) for PG (p<0.001); ADP % aggregation were 97.0 (94.5-98.2) and 37.1 (28.0-53.0) for HD and PG, respectively (p<0.001). TEG AA % aggregation was 97.8 (94.4-99.8) for HD and 13.5 (7.9-26.8) for PG (p<0.001); ADP % aggregation was 98.3 (95.3-99.9) for HD and 83.3 (77.8-87.7) for TG (p<0.001). LTA AA % aggregation was 55.0 (44.0-64.8) for HD and 0.0 (0.0-1.5) for PG (p<0.001); ADP % aggregation of 59.0 (40.8-70.8) and 14.5 (4.5-19.5) for HD and PG, respectively (p<0.001). Intra- and inter-assay imprecision estimates (CV%), respectively, in HD were 1.4 and 5.1 for Plateletworks AA, 5.5 and 15.9 for Plateletworks ADP, 3.0 and 0.0 for TEG AA, and 2.6 and 0.8 for TEG ADP. Intra-assay precision estimates for LTA AA and LTA ADP were 19.3 and 8.2. In PG, intra-assay precision was estimated as 7.0 for Plateletworks AA, 9.6 for Plateletworks ADP, 61.3 for LTA AA, 11.9 for LTA ADP, 37.6 for TEG AA, and 4.1 for TEG ADP. In our limited data set, ROC analysis showed optimal cutpoints (sensitivity/specificity) for Plateletworks AA 65.5 (1.0/1.0) and ADP 84.5 (1.0/0.90), TEG AA 87.1 (1.0/1.0) and ADP 92.7 (1.0/1.0), and LTA AA 8.75 (0.94/1.0) and ADP 25.0 (0.82/0.90) Conclusion Plateletworks most effectively distinguished % aggregation between healthy donors and patients on dual antiplatelet therapy. TEG also differentiated the groups, but differences in median ADP-induced aggregation were smaller than with Plateletworks. Both AA and ADP assays on LTA showed more variability than either Plateletworks or TEG.