RESUMEN
BACKGROUND: Our objective was to verify the reliability, internal consistency and construct validity of the Barthel Index in Brazilian cancer patients in palliative care. METHODS: We included patients with cancer, both sexes, and age greater than or equal to 18 years. We used to evaluate patients the Barthel Index, Karnofsky Performance Scale (KPS), and European Organization for Research in the Treatment of Cancer Questionnaire-core 15 (EORTC-QLQ-C15-PAL). The measurement properties evaluated in this study were test-retest and inter-rater reliability and construct validity (tested by means of correlations with other instruments). RESULTS: We included 220 patients for construct validity and a subsample of 27 patients for reliability analyses. We observed adequate reliability (intraclass correlation coefficient ≥ 0.962) and internal consistency (Cronbach's alpha = 0.942). There were adequate correlations between the Barthel Index and the KPS (rho = 0.766), and the functional capacity domain of the EORTC-QLQ-C15-PAL (rho = -0.698). CONCLUSION: The Brazilian version of the Barthel Index presents adequate test-retest and inter-rater reliability, acceptable internal consistency, and valid construct for measuring functional independence in cancer patients.