Prognostic efficacy of platelet count in patients with nonvalvular atrial fibrillation

Abstract

The prognostic efficacy of quantitative platelet activity in atrial fibrillation (AF) remains unclear. The purpose of this study was to evaluate the platelet count (PLT) as a prognostic indicator in patients with nonvalvular AF. Data on 10,978 patients with nonvalvular AF were retrieved from a prospective registry of a single medical center in Korea. Cumulative risk for stroke and bleeding events were compared between patients with normal PLT (n = 8322), mild thrombocytopenia (n = 1791), and moderate to severe thrombocytopenia (n = 865) after propensity score matching. Prediction models for stroke were derived by conventional risk factors (model 1) and by combining PLT with model 1 (model 2), and model performance was assessed by area under the receiver operator characteristics curve (AUC). During the follow-up period, 7.3%, 7.0%, and 4.5% had stroke and 7.6%, 10.8%, and 17.2% had bleeding events in the normal PLT, mild, and moderate to severe thrombocytopenia groups, respectively. Compared to the normal PLT group, the moderate to severe thrombocytopenia group showed a lower risk of stroke (hazard ratio [HR] 0.57; 95% confidence interval [CI] 0.40-0.80; P = .002). A reverse relationship was found between PLT and bleeding risk (moderate to severe thrombocytopenia: HR 2.19; 95% CI 1.77-2.70; P <.001; mild thrombocytopenia: HR 1.43; 95% CI 1.18-1.73; P <.001). Compared to model 1, model 2 showed significant improvement in risk prediction (AUC 0.628 vs 0.644; P <.001). A lower PLT was associated with a lower risk of stroke and a higher risk of bleeding events. PLT combined with conventional risk factors showed significant improvement in prediction for stroke.