Can we scientifically and reliably measure the level of consciousness in Vegetative and Minimally Conscious States? Rasch analysis of the Coma Recovery Scale Revised

Publication year: 2012
Source:Archives of Physical Medicine and Rehabilitation

Fabio La Porta, Serena Caselli, Aladar Bruno Ianes, Olivia Cameli, Mario Lino, Roberto Piperno, Antonella Sighinolfi, Francesco Lombardi, Alan Tennant

Objectives To appraise, by the mean of Rasch analysis: 1) the internal validity and reliability of the Coma Recovery Scale-Revised (CRS-R) in a sample of patients with disorder of consciousness (DOC); 2) to provide information about the comparability of CRS-R scores across persons with DOC across different settings and groups, including different etiologies. Design Multicenter observational prospective study. Setting 2 rehabilitation wards, 1 intermediate care facility and 2 nursing homes (NH) in Italy. Participants 129 consecutively admitted patients, for which assessments at 2 different time points were available, giving a total sample of 258 observations. Intervention Not applicable. Main Outcome Measure CRS-R. Results After controlling for any possible dependency between persons’ measures collected at different time points, and for uniform DIF by etiology showed by the visual subscale, Rasch analysis demonstrated adequate satisfaction of all the model’s requirements, including adequate ordering of scoring categories, unidimensionality, local independence, invariance (χ² 21=27.798; p=.146), and absence of DIF across patients’ sex, age, time and setting. The reliability (person separation index=.896) was adequate for individual person measurement. We devised practical raw score to measure conversion tables based on the CRS-R calibrations. Conclusions The CRS-R is a psychometrically sound and robust measurement tool. The linear measures of ability derived from the CRS-R total scores do satisfy all the principles of scientific measurement and are sufficiently reliable for high stakes assessments such as the diagnosis of the level of consciousness in individual patients. Future studies are needed to directly explore the capabilities of the CRS-R measures to reduce the risk of Vegetative State misdiagnosis.

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