Comparison of common outcome measures for assessing independence in patients diagnosed with disorders of consciousness: A Traumatic Brain Injury Model Systems Study

ABSTRACT Importance Patients with disorders of consciousness (DoC) after traumatic brain injury (TBI) recover to varying degrees of functional dependency. Dependency is difficult to measure but critical for outcome interpretation and prognostic counseling. Traditional outcome measures, like the Glasgow Outcome Scale-Extended (GOSE), are mandated by the US Food and Drug Administration for evaluating TBI clinical trial efficacy but have an unknown accuracy for measuring dependency. Objective We used the Functional Independence Measure (FIM) as the reference standard to evaluate how accurately the GOSE and Disability Rating Scale (DRS) assess functional dependency in the worlds largest cohort of patients with DoC after TBI. We propose an alternate, data-driven, approach to measuring dependency. Design, Setting, and Participants In this cohort study, we included patients with DoC prospectively enrolled in the longitudinal Traumatic Brain Injury Model Systems National Database (TBIMS NDB). Participants were survivors of moderate/severe TBI with DoC on admission to a US inpatient rehabilitation center between 1988 and 2020, followed 1 year after injury. Exposures We examined the classification performance of common TBI outcome measure cut-points (GOSE <=3 and <=4 [Lower and Upper Severe Disability, respectively], and DRS >=12 [Severe Disability]) in identifying subjects with functional dependency at 1 year. We compared data-derived optimal cut-points on these scales to a novel DRS-based marker of dependency, the DRSDepend. Main Outcome and Measure Total FIM score < 80 (FIM-dependency) at 1 year. Results Of 18,486 TBIMS participants, 1,483 with DoC on arrival to inpatient rehabilitation met inclusion criteria (mean [SD] age=38 [18] years; 76% male). The sensitivity of GOSE cut-points of <=3 and <=4 for identifying FIM-dependency were 97% and 98%, but specificities were 73% and 51%, respectively. The sensitivity of the DRS cut-point of >=12 was 60%, but specificity was 100%. The DRSDepend had a sensitivity of 83% and a specificity of 94% for classifying FIM-dependency, with a greater AUROC than the data-derived optimal GOSE (<=3, p=0.01) and DRS (>=10, p=0.008) cut-points. Conclusions and Relevance Commonly-used GOSE and DRS cut-points have limited sensitivity or specificity for identifying functional dependency. The DRSDepend identifies FIM-dependency more accurately than GOSE and DRS cut-points, but requires further validation.