Validation of the Brazilian Version of the Musculoskeletal Tumor Society Rating Scale for Lower Extremity Bone Sarcoma

Abstract

The Musculoskeletal Tumor Society (MSTS) rating scale is an English-language instrument used worldwide to assess functional evaluation of patients with musculoskeletal cancer. Despite its use in several studies in English-speaking countries, its validity for assessing patients in other languages is unknown. The translation and validation of widely used scales can facilitate the comparison across international patient samples. The objectives of this study were (1) to translate and culturally adapt the MSTS rating scale for functional evaluation in patients with lower extremity bone sarcomas to Brazilian Portuguese; (2) analyze its factor structure; and (3) test the reliability and (4) validity of this instrument. The MSTS rating scale for lower limbs was translated from English into Brazilian Portuguese. Translations were synthesized, translated back into English, and reviewed by a multidisciplinary committee for further implementation. The questionnaire was administered to 67 patients treated for malignant lower extremity bone tumors who were submitted to limb salvage surgery or amputation. They also completed a Brazilian version of the Toronto Extremity Salvage Score (TESS). Psychometric properties were analyzed including factor structure analysis, internal consistency, interobserver reliability, test-retest reliability, and construct validity (by comparing the adapted MSTS with TESS and discriminant validity). The MSTS rating scale for lower limbs was translated and culturally adapted to Brazilian Portuguese. The MSTS-BR proved to be adequate with only one latent dimension. The scale was also found to be reliable in a population that speaks Brazilian Portuguese showing good internal consistency (Cronbach's alpha = 0.84) and reliability (test-retest reliability and interobserver agreement of 0.92 and 0.98, respectively). Validity of the Brazilian MSTS rating scale was proved by moderate with TESS and good discriminant validity. The Brazilian version of the MSTS rating scale was translated and validated. It is a reliable tool to assess functional outcome in patients with lower extremity bone sarcomas. It can be used for functional evaluation of Brazilian patients and crosscultural comparisons.