Clinimetric testing of three self-report outcome measures for low back pain patients in Brazil: which one is the best?

STUDY DESIGN: Translation, cross-cultural adaptation, and clinimetric testing of self-report outcome measures.

OBJECTIVE: The aims of this investigation were to perform the translation and cross-cultural adaptation of the Patient-Specific Functional Scale (PSFS) into Brazilian-Portuguese and to perform a head-to-head comparison of the clinimetric properties of the Brazilian-Portuguese versions of the PSFS, the Roland-Morris Disability Questionnaire (RMDQ) and the Functional Rating Index (FRI).

SUMMARY OF BACKGROUND DATA: To date, there is no Brazilian-Portuguese version of the PSFS available and no head-to-head comparison of the Brazilian-Portuguese versions of the PSFS, RMDQ, and FRI has been undertaken.

METHODS: The PSFS was translated and adapted into Brazilian-Portuguese. The PSFS, the RMDQ, and the FRI were administered to 99 patients with low back pain to evaluate internal consistency, reproducibility, ceiling and floor effects, construct validity, internal and external responsiveness. To fully test the construct validity and external responsiveness of these measures, it was necessary to cross-culturally adapt the Pain Numerical Rating Scale and the Global Perceived Effect Scale.

RESULTS: All measures demonstrated high levels of internal consistency (Cronbach's alpha range = 0.88-0.90) and reproducibility (Intraclass Correlation Coefficient 2,1 range = 0.85-0.94). High correlations among the disability-related measures were observed (Pearson's r ranging from 0.51 to 0.71). No ceiling or floor effects were detected. The PSFS was consistently more responsive than the other measures in both the internal responsiveness and external responsiveness analyses.

CONCLUSION: The results from this study demonstrate that the Brazilian-Portuguese versions of the RMDQ, the FRI and the PSFS have similar clinimetric properties to each other and to the original English versions. Of allthe measures tested in this study the PSFS seems the most responsive. These measures will enable international comparisons to be performed, and encourage researchers to include Portuguese speakers in their clinical trials.