Coma Recovery Scale-Revised: evidentiary support for hierarchical grading of level of consciousness

Abstract

Objective: To investigate the neurobehavioral pattern of recovery of consciousness as reflected by performance on the subscales of the Coma Recovery Scale-Revised (CRS-R).

Design: Retrospective item response theory (IRT) and factor analysis.

Setting: Inpatient rehabilitation facilities.

Participants: Rehabilitation inpatients (N=180) with posttraumatic disturbance in consciousness who participated in a double-blinded, randomized, controlled drug trial.

Interventions: Not applicable.

Main outcome measures: Scores on CRS-R subscales.

Results: The CRS-R was found to fit factor analytic models adhering to the assumptions of unidimensionality and monotonicity. In addition, subscales were mutually independent based on residual correlations. Nonparametric IRT reaffirmed the finding of monotonicity. A highly constrained confirmatory factor analysis model, which imposed equal factor loadings on all items, was found to fit the data well and was used to estimate a 1-parameter IRT model.

Conclusions: This study provides evidence of the unidimensionality of the CRS-R and supports the hierarchical structure of the CRS-R subscales, suggesting that it is an effective tool for establishing diagnosis and monitoring recovery of consciousness after severe traumatic brain injury.

Keywords: Disorders of consciousness; Psychometrics; Rehabilitation; Traumatic brain injury.