Cross-Cultural Adaptation, Validity, and Reliability Study of the Turkish Version of the Back Pain Functional Scale

Study Design: Prospective study. Purpose: To investigate the cross-cultural adaptation, validity, and reliability of the Turkish version of the Back Pain Functional Scale (BPFS). Overview of literature: Low back pain is a common disorder in the population that negatively affects the patient's daily, professional, and social life. Self-report questionnaires are important to precisely evaluate back pain and making better and appropriate treatment decisions. Currently, there are several questionnaires for investigating mobility in patients with low back pain. Methods: We recruited 360 patients with chronic low back pain. For assessing the reliability of the scale, we performed test-retest and internal consistency analyses. Test-retest analysis was performed using intraclass correlation coefficient (ICC). Internal consistency was analyzed by calculating Cronbach's alpha value. Construct validity of the questionnaire was evaluated by comparing total scores on the BPFS with those on Roland Morris Disability Questionnaire (RMDQ) and Oswestry Disability Index (ODI) using Pearson's correlation coefficient analysis. Results: Cronbach's alpha value was 0.910, indicating high internal consistency. The test-retest reliability was excellent (ICC, 0.958; 95% confidence interval, 0.710-0.908). No floor or ceiling effects were observed. Factor analysis indicated that the scale had a single-factor structure. Pearson correlation coefficient was -0.669 when BPFS was compared with RMDQ and -0.701 when compared with ODI. These values indicate a significant correlation of BPFS with RMDQ and ODI. Conclusions: These data indicate the validity and reliability of the Turkish version of the BPFS.