Cross-Cultural Adaptation of the Micheli Functional Scale to Persian Language for Evaluation of Low Back Pain in the Young Athletes

Background: A clinical outcome tool is needed for the assessment of young athletes with low back pain. Objectives: To translate and culturally adapt the Micheli functional scale (MFS), a self-report questionnaire developed to evaluate young athletes with low back pain (LBP) into Persian language and examine the reliability and validity of the Persian MFS (PMFS). Materials and Methods: A cross-sectional study was conducted to assess the psychometric properties of the PMFS. The PMFS was cross- culturally adapted into Persian language adopting forward/backward translation, expert panel review, and pre-testing. The PMFS was administered to young athletes with and without LBP. Main outcome measures were Persian MFS, Persian functional rating Index (PFRI), and visual analogue scale (VAS). Results: A sample of 100 young athletes with LBP with a mean age of 16.5 ± 2.5 years participated. Fifty young athletes without LBP completed the PMFS. There was no missing responses and floor or ceiling effects. There was a significant difference for the total PMFS scores between young athletes with and without LBP. A significant correlation was found between the total PMFS score and the VAS (r = 0.92) or the PFRI (r = 0.82; P 0.001). A high internal consistency reliability (Cronbach α = 0.73), and excellent test-retest reliability (ICCagreement = 0.99, P 0.001) were demonstrated for the PMFS. Factor analysis indicated a single-factor model for PMFS scores. Conclusions: The Persian MFS is valid and reliable for use in Persian-speaking young athletes with LBP.