Abstract 521: Measurement of Platelet Retention Rate in Collagen-coated Beads Column, a Newly Developed Method to Measure Platelet Function, is Useful for Assessment of Clinical Efficacy of Dual Antiplatelet Therapy in Patients With Coronary Artery Disease
A simple, practical method to measure platelet function is unavailable for bedside use. Measurement of platelet retention rate in a collagen-coated bead column using whole blood as a sample is a new, easy-to-use assay that reflects platelet aggregate formation via GPIb-vWF interaction under high shear stress. This study examined whether this assay may be useful to assess efficacy of antiplatelet therapy.
Methods and Results: Citrated whole blood (1.5 ml) in a syringe was passed through a polyvinyl tube (2 mm diameter and 80 mm length) packed with collagen-coated beads (0.1– 0.2 mm diameter) for 40 seconds at a flow rate of 2.25 mL/min using a syringe pump. The retention rate of platelets in the column was calculated by the difference between platelet counts in blood samples before and after passage. The entire procedure takes < 5 min. As retention rate rises, so does platelet aggregability. Intra-assay coefficient of variation was < 4.0%. This platelet retention assay and the traditional optical aggregometry assay using platelet-rich plasma as a sample were performed in 247 patients with coronary artery disease (CAD). Retention rate was inhibited in patients in a steady state phase (> 1 month) of dual anti-platelet therapy (aspirin 100 mg/day plus clopidogrel 75 mg/day or ticlopidine 200 mg/day) compared with patients who were taking aspirin alone (42.6 ± 1.5 % vs. 65.5 ± 2.7 %, n = 209 and 38, respectively, p < 0.01). The platelet retention assay provided 96% of sensitivity and 90% of specificity in identifying patients with a low response to dual antiplatelet therapy, defined as < 10th percentile of platelet inhibition using the optical aggegometry assay using ADP as an agonist. During prospective follow-up (mean, 18 months) in a subgroup of 209 patients with CAD on dual antiplatelet therapy, 42 patients had a major adverse cardiac event (MACE). In multivariate Cox hazards analysis, higher platelet retention rate (> 46%, as determined by ROC analysis) was a predictor of future MACE independently of the traditional risk factors (HRs 3.2, 95%CI 1.4 to 7.3, p < 0.01).
Conclusions: Measurement of platelet retention rate in the collagen bead columns is simple and reliable and thus may be clinically useful for monitoring efficacy of anti-platelet therapy in patients with CAD.