Background: Coated-platelets, a subset of activated platelets observed with dual-agonist stimulation with collagen and thrombin, represent 30% of the platelet population in normal controls. In recently published work, we have shown that elevated coated-platelet levels (>45%) are predictive of stroke in asymptomatic carotid stenosis. We now investigate if platelet count and mean platelet volume (MPV) are related to coated-platelet levels.
Methods: Coated-platelet levels were measured in a cohort of asymptomatic outpatients referred for carotid ultrasound studies. Platelet count and mean platelet volume for each subject were recorded from the VA electronic medical record at the closest possible time period (within ≤6 months) to the date of coated-platelet sample. Correlations between each parameter and coated-platelet levels were determined and those reaching significance at p≤0.1 were included in a multiple regression model with LDL and systolic blood pressure (SBP), variables previously known to correlate with coated-platelet levels.
Results: Platelet count and mean platelet volume data were available within the specified period for 289 patients (96% male, mean age 66 years). On univariate analysis, coated-platelet levels correlated with platelet count (r = 0.15, p=0.01), but not with MPV (r=-0.04, p=0.53). When platelet count was included in a multiple regression analysis with LDL and SBP, platelet count was no longer significantly associated with coated-platelet levels. In the final model, higher coated-platelet levels were associated with LDL (p=0.008) and SBP (p=0.007) after controlling for all potentially confounding variables, including medications and comorbidities.
Conclusions: Among asymptomatic patients with carotid atherosclerosis, neither MPV, which has been previously shown to correlate with platelet aggregation, nor platelet count are significantly associated with coated-platelet levels after accounting for all potential confounding variables. These findings support the notion of coated-platelets as a unique measure of platelet procoagulant potential.