Rapid assessment of platelet function with a modified whole-blood aggregometer in percutaneous transluminal coronary angioplasty patients receiving anti-GP IIb/IIIa therapy.

BACKGROUND

The glycoprotein (GP) IIb/IIIa receptor antagonist abciximab (c7E3 Fab, ReoPro) is approved for use in high-risk percutaneous transluminal coronary angioplasty (PTCA). At present, no "point of care" exists for measuring pharmacological GP IIb/IIIa blockade. To address this need, the Chrono-log Whole Blood Aggregometer, which measures platelet aggregation by electrical impedance, was adapted to test platelet function at the bedside.

METHODS AND RESULTS

GP IIb/IIIa receptor blockade, impedance (5 microg/mL collagen), and turbidimetric aggregation (5 and 20 micromol/L ADP) measurements were obtained on 14 PTCA patients who received the standard bolus plus a 12-hour infusion of abciximab. During abciximab administration, mean GP IIb/IIIa receptor blockade was > 91%, and both impedance and turbidimetric aggregation were inhibited by > or = 90%. At 12 hours after abciximab treatment, the mean inhibition of turbidimetric platelet aggregation to 5 and 20 micromol/L ADP was 65+/-20% and 49+/-14%, respectively, and inhibition of impedance aggregation was 69+/-12%. GP IIb/IIIa receptor blockade was 67+/-8%. At 36 hours after abciximab treatment (n=8), the mean inhibition of turbidimetric platelet aggregation to 5 and 20 micromol/L ADP was 44+/-21% and 30+/-14%, respectively, whereas impedance aggregation was inhibited by 60+/-14%. GP IIb/IIIa receptor blockade was 57+/-7%.

CONCLUSIONS

During and at 12 hours after abciximab therapy, impedance and turbidimetric platelet aggregation to 5 micromol/L ADP were comparable and closely correlated with GP IIb/IIIa receptor blockade. However, at 36 hours after abciximab treatment, impedance platelet aggregation more closely paralleled GP IIb/IIIa receptor blockade and indicated a slower recovery of platelet function than turbidimetric aggregometry.