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

Abstract

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 three ASA dosing regimens in 24 T2D patients randomized in a three-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 as follows: light transmission aggregometry (LTA)–0.5 mg/mL of arachidonic acid (AA) and 10 µM adenosine diphosphate (ADP); multiplate whole blood aggregometry (WBA)–0.5 mM AA and 6.5 µM ADP; platelet function analyzer (PFA)-100™–collagen and ADP (CADP) and collagen and epinephrine (CEPI); VerifyNow™–ASA; and 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 as follows: very good–LTA-AA (k = 0.95) and VerifyNow™-ASA (k = 0.85); good–serum TxB₂ (k = 0.79); moderate–LTA-ADP (k = 0.59), PFA-100™-CEPI (k = 0.56), urinary TxB₂ (k = 0.55), WBA-AA (k = 0.47); and poor–PFA-100™-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 as follows: very good–VerifyNow™-ASA (k = 0.81, R² = 0.56) and LTA-AA (k = 0.85, R² = 0.65); good–PFA-100^TM-CEPI (k = 0.62, R² = 0.30); moderate–urinary TxB₂ (k = 0.57, R² = 0.51) and LTA-ADP (k = 0.47, R² = 0.56); fair–WBA-AA (k = 0.31, R² = 0.31); and poor–PFA-100™-CADP (k = 0.04, R² = 0.003) and 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.

Keywords:

• Aspirin
• platelet function
• type 2 diabetes

Acknowledgments

The trial was sponsored by the University of Oxford. It was conducted and analyzed independently by the University of Oxford Diabetes Trials Unit. Active and placebo study medication was provided by Bayer AG. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.

PH, MAB, and RRH take responsibility for the contents of this article. They made substantial contributions to the protocol conception and design. All the authors made substantial contributions to the acquisition, analysis, or interpretation of the data. PH drafted the manuscript, and all the authors revised it for intellectual content and approved the final version. RD performed some advice and statistical analysis and produced the final figures used in the manuscript. All the authors agree to be accountable for all aspects of the work to ensure the accuracy and integrity of the data.

Declaration of interest statement

RRH is a NIHR Senior Investigator and has received research support from Bayer, Merck, and Novartis. He has attended advisory boards of Amylin, Lilly, Merck, Novartis, and Novo Nordisk and has given lectures supported by Bayer, Lilly, Merck, and Novo Nordisk. MAB receives research funding from Novartis and Bayer. PH is an ex-consultant for Sysmex UK and has previously received research funding from Siemens Diagnostics and Lilly when he was employed by Oxford University NHS Trust until 2012.

Additional information

Funding

This work was supported by the British Heart Foundation [PG/11/29/28852].