How to test the effect of aspirin and clopidogrel in patients on dual antiplatelet therapy?

Abstract

Dual antiplatelet therapy with clopidogrel and aspirin is frequently used for the prevention of recurrent ischemic events. Various laboratory methods are used to detect the effect of these drugs administered in monotherapy, however their value in dual therapy has not been explored. Here, we determined which methods used for testing the effect of clopidogrel or aspirin are influenced by the other antiplatelet agent. One arm of the study included 53 ischemic stroke patients being on clopidogrel monotherapy showing effective inhibition of the P2Y₁₂ ADP receptor. Laboratory tests routinely used for the detection of aspirin resistance (arachidonic acid (AA)-induced platelet aggregation/secretion, AA-induced thromboxane B₂ (TXB₂) production in platelet-rich plasma and VerifyNow Aspirin assay) were carried out on samples obtained from these patients. The other arm of the study involved 52 patients with coronary artery disease being on aspirin monotherapy. Methods used for testing the effect of clopidogrel (ADP-induced platelet aggregation and secretion, flow cytometric analysis of vasodilator-stimulated phosphoprotein (VASP) phosphorylation and a newly developed P2Y₁₂-specific platelet aggregation (ADP[PGE₁] test)) were performed on samples obtained from these patients. Clopidogrel monotherapy significantly inhibited AA-induced platelet aggregation and secretion, moreover, AA-induced TXB₂ production was also significantly decreased. VASP phosphorylation and AA-induced platelet aggregation showed fair correlation in patients taking clopidogrel only. Clopidogrel did not inhibit the VerifyNow Aspirin test significantly. Aspirin monotherapy influenced ADP-induced platelet aggregation and secretion, but did not have an effect on VASP phosphorylation and on the ADP[PGE₁] platelet aggregation test.

• Anti-platelet drug
• aspirin
• clopidogrel
• drug resistance
• platelet aggregation

Acknowledgements

The authors would like to thank Prof. János Kappelmayer for providing flow cytometer for the experiments and Valéria Kissné Sziráki for helpful technical assistance.

Declaration of interest

The authors report no conflict of interest.

The work was supported by the National Office for Research and Technology DE-LABDIA Jedlik Ányos program, by the National Research Fund (OTKA K109712, PD111929), by the Hungarian Academy of Sciences (MTA11003, TKI227) and by the National Development Agency (TÁMOP project 4.2.2.A-11/1/KONV-2012-0045). Z. Bagoly is the recipient of János Bólyai fellowship and Lajos Szodoray Prize.