Translation, cross-cultural adaptation, and measurement properties of the Back pain knowledge and beliefs survey (BacKS) for the Brazilian population

BACKGROUND: Low back pain (LBP) is a highly prevalent and disabling health condition worldwide. A Patient-Reported Outcome Measure (PROM) to assess people's knowledge and beliefs about LBP was recently developed in Australia, but a Brazilian-Portuguese translation is not yet available. The lack of adequate cross-cultural adaptation of questionnaires is a barrier to developing LBP research and clinical practice in different cultures. OBJECTIVE: To translate, cross-culturally adapt, and test the measurement properties of the Back pain Knowledge and beliefs Survey (BacKS) to allow its use with Portuguese-speaking Brazilians with LBP (BacKS-BR). METHODS: A forward and backward translation was performed, and measurement properties of the BacKS-BR were assessed following the COSMIN guidelines. Pilot testing was performed to assess content validity and online surveys were undertaken to assess other measurement properties. Structural validity was evaluated by confirmatory factor analysis (CFA) and cross-cultural validity by multigroup CFA. Construct validity was assessed by correlation between BacKS-BR and the Back Beliefs Questionnaire and a positive moderate correlation was expected. Internal consistency was assessed by Cronbach's alpha, reliability by intra-class correlation coefficient, and measurement error by calculating the smallest detectable change (SDC). RESULTS: BacKS-BR had good content validity and the 2-factors structure was confirmed. Multigroup CFA produced acceptable measurement invariance. Pearson test confirmed our construct validity hypothesis (0.59). Internal consistency and reliability were adequate (>0.70) and SDC was 11.09 for total scale. CONCLUSION: The BacKS was successfully translated into Brazilian-Portuguese and proved to have adequate measurement properties. Its use is recommended for research and clinical purposes.