The Glasgow Coma Scale: a critical appraisal of its clinimetric properties.

The Glasgow Coma Scale is a commonly used instrument in clinical practice. This article examines the published evidence to assess whether the scale possesses the requisite clinimetric properties. Articles describing and using the scale were located through a MEDLINE search. The clinimetric properties of the scale were appraised using the methodological principles of sensibility, reliability, validity, and responsiveness. The scale has a good sensibility and reliability (intraclass correlation coefficient, 0.8 to 1 for trained users). It has a well-established cross-sectional construct validity. Its predictive validity in traumatic coma, when combined with age and brainstem reflexes, is good in the generating sample (sensitivity, 79 to 97%; specificity, 84-97%) but has not been tested in an external validation sample. Its longitudinal construct validity has not been studied adequately. Thus, the scale is an established discriminative instrument but its validity as a predictive and an evaluative instrument has not yet been studied adequately.