Measurement Properties of the Barthel Index in Geriatric Rehabilitation

Objective: The Barthel index (BI) is a widely used observer-based instrument to measure physical function. Our objective is to assess the structural validity, reliability, and interpretability of the BI in the geriatric rehabilitation setting. Design: Two studies were performed. First, a prospective cohort study was performed in which the attending nurses completed the BI at admittance and discharge (n = 207). At discharge, patients rated their change in physical function on a 5-point Likert rating scale. To assess the internal structure of the BI, a confirmatory factor analysis was performed. Unidimensionality was defined by comparative fit index and Tucker-Lewis index of > 0.95, and root mean square error of approximation of < 0.06. To evaluate interpretability, floor/ceiling effects and the minimal important change (MIC) were assessed. Predictive modeling was used to calculate the MIC. The MIC was defined as going home and minimal patientreported improvement defined as slightly or much improved physical function, which served as anchors to obtain a clinical-and patient-based MIC. A second group of 37 geriatric rehabilitation patients were repeatedly assessed by 2 attending nurses to assess reliability of the BI. The intraclass correlation coefficient, standard error of measurement, and smallest detectable change were calculated. Setting and Participants: Patients receiving inpatient geriatric rehabilitation admitted to 11 Dutch nursing homes (n = 244). Results: Confirmatory factor analysis showed partly acceptable fit of a unidimensional model (comparative fit index 0.96, Tucker-Lewis index 0.95, and root mean square error of approximation 0.12). The clinical-based MIC was 3.1 [95% confidence interval (CI) 2.0-4.2] and the patient-based MIC was 3.6 (95% CI 2.8-4.3). The intraclass correlation coefficient was 0.96 (95% CI 0.93-0.98). The standard error of measurement and smallest detectable change were 1.1 and 3.0 points, respectively. Conclusions/Implications: The structural validity, reliability, and interpretability of the BI are considered sufficient for measuring and interpreting changes in physical function of geriatric rehabilitation patients. (C) 2018 AMDA - The Society for Post-Acute and Long-Term Care Medicine.