['To date, infections have usually been associated with elevations of the mean platelet volume. We correlated infection with respiratory syncytial virus (RSV) with changes in mean platelet volume (MPV).', 'A consecutive series of patients with positive and negative rapid RSV assays and viral cultures, as well as children under 10 years of age with bronchoscopy for pneumonia or airway obstruction, were compared.', 'The MPV was significantly lower in patients with positive versus negative rapid RSV assays (9.7±0.8 vs. 10.5±0.9 fl, p<0.001), as well as viral cultures (9.9±1.0 vs. 10.5±1.0 fl, p<0.001). Children with RSV undergoing bronchoscopy (n=7) also had significantly lower MPV than children without RSV (n=79) (8.8±1.0 vs. 10.2±1.1 fl, p<0.004). An MPV <8.9 fl had a sensitivity of 71% and specificity of 49% for RSV in children undergoing bronchoscopy.'] Is respiratory syncytial virus infection strongly correlated with decreased mean platelet volume?