LAUSR

BACKGROUND There is a tremendous clinical and research need to bridge the gap between disorder of consciousness and functional independence scales with a single unidimensional measure in people with acquired brain injury. AIM To calibrate an essentially unidimensional subset of items from the Italian Early Functional Abilities (EFA), demonstrating internal construct validity and sufficient reliability for individual patient measurement. DESIGN Multicenter observational cross-sectional study. SETTING Inpatients from 11 different Italian Rehabilitation centers. POPULATION Three hundred sixty-two adult patients with a disorder of consciousness due to an acquired brain injury. METHODS The Italian version of EFA was administered to the sample and then submitted to Mokken analysis, Confirmatory Factor Analysis, Rasch analysis, Confirmatory Bifactor Analysis, and external construct validity. RESULTS According to Mokken Analysis (all item scalability coefficients Hj positive; all item-pair scalability coefficients Hij >0.3; scale coefficient H=0.762), and Confirmatory Factor Analysis (RMSEA=0.081; SRMR=0.048; CFI=0.995; TLI=0.995), the Italian EFA showed a sufficient preliminary unidimensionality. Within Rasch Analysis, a final 12-item solution for the EFA (EFA-R) was calibrated. EFA-R is “essentially unidimensional” according to the following requirements: 1) analysis of residual correlations which supported item essential local independence; 2) a robust correlation between item subtests (rho=0.950); 3) only 2.1% of cases with significant difference between person parameter estimates by different subscales; 4) an explained common variance equal to 0.916 obtained from a final Confirmatory Bifactor Analysis. It also satisfied invariance requirement (unconditional χ220=9.81; P=0.457, conditional class-interval based χ235=33.1; P=0.557), and monotonicity. The reliability (Person Separation Index=0.887) was adequate for person measurements. A practical raw-score-to-measure conversion table based on the EFA-R calibration was devised. Finally, EFA-R strongly correlated with Coma Recovery Scale-Revised (rho=0.922) and motor FIM™ (rho=0.808). CONCLUSIONS EFA-R is an essentially unidimensional subset of 12 items with adequate internal construct validity and sufficient reliability for individual patient measurement under the Rasch Model Theory framework. CLINICAL REHABILITATION IMPACT EFA-R has the potential to measure people’s functional abilities whose consciousness is improving despite ongoing severe motor-functional impairments during the early stages of rehabilitation. It provides “a measurement bridge” between the disorder of consciousness and the functional independence scales in patients with severe acquired brain injury.