RESUMO
Abstract Background: The Functional Index for Hand Osteoarthritis (FIHOA) is a simple, reliable, and reproducible specific instrument to evaluate hand OA that can be applied both in clinical practice and research protocols. In order to be used in Brazil, FIHOA has to be translated into Portuguese, culturally adapted and have the reliability of the translated FIHOA version tested, which is the purpose of this study. Methods: The FIHOA was translated into Brazilian Portuguese and administered to 68 patients with hand OA recruited between May 2019 and February 2020. The test-retest was applied to 32 patients and the reliability was assessed using Spearman's correlation coefficient and intraclass correlation coefficient (ICC). The internal consistency reliability was evaluated using Cronbach's alpha. External construction validity was assessed using the Spearman's correlation test between FIHOA and pain, assessed with a Visual Analogue Scale (VAS), the Cochin Hand Functional Scale (CHFS) and Health Assessment Questionnaire (HAQ). Results: The 30 participants that initially answered the translated version of the FiHOA did not report difficulties in understanding or interpreting the translated version. The test-retest reliability for the total score was strong ( r =0.86; ICC = 0.89). Mean differences (1.37 ± 0.68) using Bland Altman's analysis did not significantly differ from zero and no systematic bias was observed. Cronbach's alpha was also high (0.89) suggesting a strong internal coherence in the test items. There were also correlations between FIHOA and the CHFS ( r =0.88), HAQ ( r = 0.64) and pain in the hands both at rest ( r =0.55) and in motion ( r =0.44). Conclusion: The translation of the FIHOA into Brazilian Portuguese proved a valid instrument for measuring the functional capacity of patients with hand OA who understand Brazilian Portuguese.