Examining the Association Between States of Consciousness and the Coma Recovery Scale–Revised: A Rasch Analysis

PURPOSE: Occupational therapists use the Coma Recovery Scale Revised (CRSR) to evaluate and make treatment decisions for individuals with disorders of consciousness (DoC) following a brain injury. Six subscales comprise the CRSR: auditory, visual, motor, verbal, communication, and arousal. Each subscale includes rating scale steps and some of these align to states of consciousness (state) as determined by existing consensus-criteria. States include: comatose, vegetative state (VS), minimally conscious state (MCS), and emerging MCS (eMCS). Individuals with DoC are frequently misdiagnosed (40-70%). The purpose of this study is to empirically examine the association between CRSR subscales and state of consciousness.

DESIGN: Retrospective cohort study using the Rasch partial credit model, evaluated the CRSR subscales and rating scale steps hierarchy. CRSR data came from four cohorts: two clinical trials (n = 192) and two rehabilitation centers (n = 72). All participants were adults (> 18 years) in DoC following a brain injury, receiving treatment (e.g. clinical trial or rehabilitation center), and assessed using the CRSR. Participants had repeated CRSR assessments (n = 1142 records). State was recorded for 184 participants who were part of a clinical trial. Three state-level variables were available: clinician-reported, consensus-based state, and Rasch-derived; each categorized participants’ as VS, MCS, or eMCS.

METHOD: CRSR ordinal raw scores were transformed into equal interval measures using Rasch Measurement. Rasch Measurement generated a hierarchy of subscales from Verbal to Communication. The rating scale steps and subscales were anchored in place and the three additional state variables were included in the hierarchy. In this way, categories for each state variable are associated with different regions of the CRSR Rasch measure.

RESULTS: CRSR transformed subscales ranged from -6.52 to 5.85 logits. After anchoring, clinician-reported state variable indicated patients were VSv< -1.68 logits and MCS > -1.68 logits. Consensus-based state variable indicated patients were: VS < -1.23, -1.23 < MCS < 2.49, and eMCS > 2.49 logits. Rasch-derived state indicated patients were: VS < -3.19, -3.19 < MCS < 1.77, and eMCS > 1.77. The hierarchical order of the subscale steps indicated that, relative to the consensus criteria and clinician-observed state variables, steps 0 for communication, 4 for auditory, 3 for arousal, and steps 2 and 3 for verbal, were mislabeled. Relative to categorizing patients, consensus-based and Rasch-derived approaches agree on categorization of patients with eMCS (100% agreement). There was significant disagreement in categorizing patients with MCS and VS between consensus-based and Rasch-derived variables (p < 0.001, Fisher’s Exact Test). Specifically, of 711 categorized at MCS by consensus-based criteria 95 (13%) were categorized as eMCS; of 506 VS consensus-based participants, 327 (65%) were categorized as MCS on the data-driven variable.

CONCLUSION: This analysis validated the hierarchy of the CRSR subscales but also demonstrated current consensus criteria may significantly misclassify participants as less conscious than they may be. The Rasch-derived variable classifies participants as more conscious than the consensus-based criteria and may address the frequency of misdiagnosis in these patients. Diagnosis of state informs prognosis and decisions for rehabilitation services.

IMPACT STATEMENT: The Rasch-derived state variable may impact conversations therapists have with the rehabilitation team and families about the patient’s plan of care. Identifying appropriate state will assist occupational therapists in using assessment results more effectively to plan and advocate for occupational therapy treatment.

References

Bond, T. G., & Fox, C. M. (2015). Applying the Rasch Model Fundamental Measurement in the Human Sciences (Third edition ed.). New York, NY: Taylor & Francis.

Giacino, J. T., Katz, D. I., Schiff, N. D., Whyte, J., . . . Armstrong, M. J. (2018). Practice Guideline Update Recommendations Summary: Disorders of Consciousness: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology; the American Congress of Rehabilitation Medicine; and the National Institute on Disability, Independent Living, and Rehabilitation Research. Arch Phys Med Rehabil, 99(9). https://doi.org/10.1016/j.apmr.2018.07.001

Giacino, J. T., Whyte, J., Nakase-Richardson, R., Katz, D. I., . . . Zasler, N. (2020). Minimum Competency Recommendations for Programs That Provide Rehabilitation Services for Persons With Disorders of Consciousness: A Position Statement of the American Congress of Rehabilitation Medicine and the National Institute on Disability, Independent Living and Rehabilitation Research Traumatic Brain Injury Model Systems. Arch Phys Med Rehabil, 101(6), 1072-1089. https://doi.org/10.1016/j.apmr.2020.01.013s

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