Psychometric properties of the Italian version of the Barthel Index in patients with Parkinson's disease: a reliability and validity study

The Barthel Index (BI) is used in Italy to measure the severity of disability and to identify patients suitable for admission to rehabilitation units. The objective of this psychometric study was to validate the Italian version of the BI in a population of patients with Parkinson's disease (PD). The study was conducted at three neurological and rehabilitation centres in Rome, Italy. The BI was administered to outpatients with PD. The reliability of the scale was assessed using Cronbach's alpha for internal consistency: the intra-class correlation coefficient (ICC) was used to measure its intra- and inter-rater reliability. Pearson's correlation coefficient was calculated to evaluate its validity, comparing it with the Parkinson's disease Questionnaire (PDQ-39), the Italian version of the Geriatric Depression Scale (GDS), the Hospital Anxiety and Depression Scale (HADS), and the Short Form 36-Health Survey Questionnaire (SF-36). The BI was administered to 94 patients with PD. The psychometric properties measured were significant: Cronbach's alpha was 0.866 and the ICC for intra- and inter-rater reliability was 0.998 and 0.993, respectively. Pearson's correlation coefficient showed good correlation with the PDQ-39, GDS, HADS and SF-36 (p < 0.01). The BI is a valid and reliable tool for measuring disability in a PD population.