Cross-cultural adaptation and validation of the Brazilian Portuguese version of the neck disability index and neck pain and disability scale

Study Design. This study's design was a cross-cultural validation of the Neck Disability Index and Neck Pain and Disability Scale. Objectives. This study's objective was to translate, culturally adapt, and validate a Brazilian Portuguese version of the Neck Disability Index (NDI-BR) and the Neck Pain and Disability Scale (NPDS-BR). Summary of Background Data. Although several valid measures exist for measurement of neck pain and functional impairment, these measures have yet been validated in Brazilian Portuguese. Successful linguistic and cultural translation may allow appropriate cross-cultural comparison for clinical and laboratory research analysis. Methods. The NDI-BR and NPAD-BR were culturally and linguistically translated from English into Brazilian Portuguese. The translated version of the instrument was administered to 203 patients at a midsize hospital in southern Brazil. Psychometric evaluation included factor analysis, internal reliability measures, test-retest reliability at 1 and 7 days, and criterion validity comparison with the Brazilian version of the SF-36. Results. Factor analyses demonstrated a single-factor subscale for the NDI-BR and three subscales for the NPDS-BR. An item analysis showed a high degree of internal consistency for the NDI-BR (r = 0.74) and the three subscales of the NPDS-BR (subscale 1, r = 0.89; subscale 2, r = 0.81; subscale 3, r = 0.72). Test-retest reliability was also acceptable at for the NDI-BR (0.98 at baseline and 0.48 at 7 days) and subset one (0.96 at baseline and 0.91 at 7 days), subset 2 (0.96 at baseline and 0.62 at 7 days), and subset 3 (0.52 at baseline and 0.45 at 7 days) of the NPDS-BR. Construct validity was established during comparison of the Brazilian version of the SF-36. Only items associated with physical role, bodily pain, and emotional role failed significant correlation. Conclusions. A reliable and valid Portuguese version of the Neck Disability Index and Neck Pain and Disability Scale was developed, which will facilitate the examination of functional performance within a large patient population, as well as cross-cultural comparisons.