Comparison of nine platelet function tests used to determine responses to different aspirin dosages in people with type 2 Diabetes: platelet function testing in type 2 Diabetes

The antiplatelet efficacy of aspirin (ASA) is reduced in type 2 diabetes (T2D). As the best ex-vivo method of measuring ASA efficacy remains uncertain, we compared nine platelet function tests to assess responsiveness to 3 ASA dosing regimens in 24 T2D patients randomized in a 3-treatment crossover design to ASA 100 mg/day, 200 mg/day or 100 mg twice daily for 2-week treatment periods. Platelet function tests compared were: Light transmission aggregometry (LTA-0.5mg/ml of arachidonic acid (AA) and 10 µM ADP); Multiplate whole blood aggregometry (WBA-0.5mM AA and 6.5µM ADP); PFA-100TM-CADP and CEPI; VerifyNowTM-ASA; Urinary 11-dehydro-thromboxane B2 (TxB2) and Serum TxB2. All cyclo-oxygenase (COX-1) dependent tests and some COX-1 independent tests (PFA-CEPI, LTA-ADP) demonstrated significant reductions in platelet reactivity with all ASA doses. Two COX-1 independent tests (WBA-ADP and PFA-CADP) showed no overall reduction in platelet reactivity. Overall classifications for detecting all ASA doses, compared to baseline, were: Very good-LTA-AA (k=0.95) and VerifyNowTM-ASA (k=0.85); Good-Serum TxB2 (k=0.79); Moderate-LTA-ADP (k=0.59), PFA-100TM-CEPI (k=0.56), Urinary TxB2 (k=0.55), WBA-AA (k=0.47); Poor-PFA-100TM-CADP (k=-0.02) and WBA-ADP (k=-0.07). No significant kappa statistic differences were seen for each test for each ASA dose. Correlations for each test with serum TxB2 measurements were: Very good - VerifyNowTM-ASA (k=0.81, R2=0.56), LTA-AA (k=0.85, R2=0.65); Good-PFA-100TM-CEPI (k=0.62, R2=0.30); Moderate-Urinary TxB2 (k=0.57, R2=0.51), LTA-ADP (k=0.47, R2=0.56); Fair-WBA-AA (k=0.31, R2=0.31) and Poor-PFA-100TM-CADP (k=0.04, R2=0.003), WBA-ADP (k=-0.04, R2=0.0005). The platelet function tests we assessed were not equally effective in measuring the antiplatelet effect of ASA, and correlated poorly amongst themselves but COX-1 dependent tests performed better than non-COX-1 dependent tests.