Utility of a whole blood single platelet counting assay to monitor the effects of tirofiban in patients with acute coronary syndromes scheduled for coronary intervention

Summary

This study aimed to establish the utility of a whole-blood singleplatelet counting (WBSPC) assay, a measure of microaggregation, in monitoring the effects of tirofiban, comparing this with optical aggregometry (OA) and the Ultegra TRAP cartridge system (UTC), measures of macroaggregation. Fifty-nine patients with acute coronary syndrome scheduled for coronary angiography +/angioplasty were studied. WBSPC assay (ADP 0.3-100 µM, Sysmex KX21 analyzer), OA (ADP 20 µM) and UTC were performed: before starting tirofiban; 30 min, 4 and 24 h after starting tirofiban; and 1 and 2h after stopping tirofiban. Thirty minutes after starting tirofiban, there was substantial inhibition of platelet aggregation (40 ± 30%; WBSPC, 2 minutes after addition of ADP 30 µM) and this remained stable at 4 and 24 h. OA (86 ± 17%; inhibition of maximal aggregation,ADP 20 µM) and UTC (93 ± 7%) showed marked inhibition with less inter-individual variation. There was no significant correlation between OA and UTC results (R2 = 0.006), but fair correlation between OA and WBSPC results (R2 = 0.37). Greater inhibition of macroaggregation (OA and UTC) was seen compared to microaggregation (WBSPC) such that WBSPC was more discriminating in the therapeutic range when macroaggregation was often completely inhibited. A WBSPC assay of platelet microaggregation shows promise for monitoring GPIIb/IIIa antagonists.

Keywords

Platelets - tirofiban - whole blood single platelet count - microaggregation

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