Interrater reliability of Glasgow Coma Scale scores in the emergency department

Study objective: Emergency physicians often use the Glasgow Coma Scale (GCS) to help guide decisions in patient care, yet the reliability of the GCS has never been tested in a typical broad sample of emergency department (ED) patients. We determined the interrater reliability of the GCS between emergency physicians when adult patients with altered levels of consciousness are assessed. Methods: In this prospective observational study at a university Level I trauma center, we enrolled a convenience sample of ED patients older than 17 years who presented with an altered level of consciousness. Two residency-trained attending emergency physicians independently assessed and recorded the GCS score and its components (eye, verbal, and motor) in blinded fashion within a 5-minute period. Data were analyzed for interrater reliability by using standard ordinal calculations. We also created scatter plots and Bland-Altman plots for each GCS component and for the GCS score. Results: One hundred thirty-one patients were screened and enrolled in the study, with 15 excluded because of protocol violations. Of the 116 remaining patients, the agreement percentage for exact total GCS was 32% (tau-b=0.739; Spearman rho=0.864; Spearman rho(2)=75%). Agreement percentage for GCS components were eye 74% (tau-b=0.715; Spearman rho=0.757; Spearman rho(2)=57%), verbal 55% (tau-b=0.587; Spearman rho=0.665; Spearman rho(2)=44%), and motor 72% (tau-b=0.742; Spearman rho=0.808; Spearman rho(2)=65%). Our Spearman's analyses found that only approximately half (44% to 65%) of the observed variance could be explained by the relationship between the paired component measures. For GCS components, only 55% to 74% of paired measures were identical, and 6% to 17% of them were 2 or more points apart. Conclusion: We found only moderate degrees of interrater agreement for the GCS and its components.