The Coma Recovery Scale-Revised: Evidentiary Support for Hierarchical Grading of Level of Consciousness

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Study examined the construct validity of the subscales of the Coma Recovery Scale-Revised (CRS-R) in measuring the neurobehavioral pattern of recovery of consciousness. Item response theory (IRT) and factor analyses were applied to CRS-R subscales scores collected from 180 rehabilitation inpatients with posttraumatic disturbance in consciousness who participated in a double-blinded, randomized, controlled drug trial. 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. The CRS-R adhered to the 4 critical scaling criteria of unidimensionality, monotonicity, mutual independence, and equivalent loadings of all items. These results support the hierarchical structure of the CRS-R and suggest that it is an effective tool for establishing diagnosis and monitoring recovery of consciousness after severe traumatic brain injury.

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