Monitoring ASA and P2Y12-specific platelet inhibition--comparison of conventional (single) and multiple electrode aggregometry.

OBJECTIVE: Several platelet function test systems exist for the evaluation of the platelet inhibitory effect in patients on P2Y12 inhibitors and/or acetylsalicylic acid (ASA, aspirin) therapy. Studies comparing different available assays found only a poor correlation. The objective of the present study was to evaluate the correlation and agreement between single electrode (SEA) and multiple electrode (MEA) aggregometry. METHODS AND RESULTS: In whole blood arachidonic acid (AA) and adenosine diphosphate (ADP)-induced platelet aggregation was measured simultaneously using SEA (Chrono-Log) and MEA (Multiplate). We analyzed a total of 226 measurements taken from 58 patients on single ASA therapy or dual antiplatelet therapy with ASA and a thienopyridine. A cut-off value for clopidogrel/prasugrel high on-treatment platelet reactivity (HPR) of > 47 units (U) was chosen for MEA testing using hirudin and > 5 Ohm for SEA with citrate anticoagulated blood samples. The respective cut-off values for ASA HPR were > 30 U for the MEA assay and > 1 Ohm for SEA testing. There was a good correlation of the prevalence of thienopyridine-HPR in both whole blood assays (Spearman rank correlation coefficient r = 0.698) and a good inter-rate accordance (Cohen's Kappa statistic κ = 0.648). For AA-induced aggregation, the correlation of the results obtained was significant (r = 0.536; p < 0.001) and detecting ASA-HPR revealed a moderate (κ = 0.482) correlation between both impedance aggregometry assays. CONCLUSION: Platelet function testing using SEA and MEA provided both good accordance and correlation and therefore study results obtained by these two assays similarly enabled the detection of HPR of thienopyridine (and ASA) therapy.

Comparing the antiplatelet effect of clopidogrel hydrogensulfate and clopidogrel besylate: a crossover study.

BACKGROUND: Clopidogrel hydrogensulfate is a thienopyridine acting as an important antiplatelet agent alone or in combination with acetyl salicylic acid to prevent cardiovascular complications. A different clopidogrel salt, clopidogrel besylate, was approved in Germany as a "new drug" in May 2008. Only one study with 46 healthy men compared the plasma concentrations of both clopidogrel formulas. In our crossover study we measured the antiplatelet effect of clopidogrel hydrogensulfate (CHS, clopidogrel bisulfate) and clopidogrel besylate (CB) using two techniques, whole blood impedance aggregometry and flow cytometry in healthy subjects. METHODS: Twenty-one healthy volunteers (14 male, 7 female, mean age 36.3 years) were treated either with CHS or CB (300 mg loading, followed by 75 mg/day) and after a wash-out period of at least 21 days, the participants were switched to the other clopidogrel salt in a crossover design. Blood samples were drawn before and 2, 4 and 48 h after the initial dose was taken. Flow cytometry measurements of CD62P (P-selectin) expression were done at baseline and 48 h thereafter with three different ADP concentrations (5, 15, 50 micromol/L ADP). Whole blood impedance aggregometry testing (Chrono-log Model 590) was performed at baseline and after 2, 4 and 48 h with two ADP concentrations (5 and 20 micromol/L ADP). RESULTS: Using flow cytometry, the mean inhibitory effect of clopidogrel on the CD62P expression was similar and no significant differences were noted in subjects treated with either of the clopidogrel formulas for hydrogensulfate or besylate salt (5 micromol/L ADP: 8.12 +/- 5.53 CHS vs. 6.48 +/- 5.01 CB; 15 micromol/L ADP: 9.33 +/- 6.44 CHS vs. 8.99 +/- 8.27 CB; 50 micromol/L ADP: 11.17 +/- 6.81 CHS vs. 9.52 +/- 6.17 CB). It is important to note that clopidogrel CB shows similar and conspicuously high interindividual variability as was reported earlier on CHS. We observed both possibilities, subjects responding less to the hydrogensulfate salt, but better to the besylate salt, and vice versa. Using aggregometry, both salt formulas achieved similar inhibitory effects regarding initial platelet function (2 h/5 micromol/L ADP: CHS 4.5 +/- 3.66 Omega; CB 3.89 +/- 3.81 Omega and 4 h/5 micromol/L ADP: CHS 5.78 +/- 3.51 Omega; CB 4.89 +/- 4.03 Omega) as well as during the maintenance phase (48 h/5 micromol/L ADP: CHS 2.86 +/- 2.92 Omega; CB 3.43 +/- 3.06 Omega). Once again the aggregometry results for CB showed a similarly high interindividual variability as also holds true for CHS. Some subjects had a better antiplatelet effect with clopidogrel besylate and vice versa with clopidogrel hydrogensulfate. CONCLUSION: The crossover study using whole blood aggregometry and flow cytometry shows no overall significant difference in the antiplatelet effect of clopidogrel hydrogensulfate as compared to clopidogrel besylate. However, it is important to note that besides high interindividual there is also high intraindividual variability between the two different clopidogrel formulas. We observed both: subjects responding less to besylate salt, but better to hydrogensulfate salt, and vice versa.