Study design: Prospective study.
Objective: To evaluate the reliability and validity of the adapted Korean version of the Quebec Back Pain Disability Scale (QDS).
Summary of background data: The Korean version of the QDS has not been validated.
Methods: Translation/retranslation of the English version of QDS was conducted, and all steps of the cross-cultural adaptation process were performed. The Korean version of the Visual Analog Scale (VAS) measure of pain, QDS and the previously validated Oswestry Disability Index (ODI) and Short Form-36 (SF-36) were mailed to 100 consecutive patients with chronic low back pain of at least 3 months duration. Eighty patients responded to the first mailing of questionnaires and 59 of the first time responder returned their second survey. The average age of the 59 patients (39 female, 20 male) was 48.0 years. Reliability assessment was determined by estimating κ statistics of agreement for each item, the intraclass correlation coefficient (ICC) and the Cronbach α. Concurrent and construct validity was evaluated by comparing the responses of QDS with the results of VAS and responses of ODI and SF-36 by using the Pearson correlation coefficient.
Results: The constructed Bland Altman plot showed a good reliability. All items had a κ statistics of agreement > 0.6. The QDS showed excellent test/retest reliability as evidenced by the high ICC for both assessments (ICC = 0.9094; P < 0.001). Internal consistency was found to be very good at both assessments with the Cronbach α (0.9172 and 0.9319 at first and second assessments, respectively). The QDS was correlated with the VAS (r = 0.647; P < 0.001 and r = 0.609; P < 0.001 at first and second assessments, respectively) and with the ODI (r = 0.718; P < 0.001 and r = 0.690; P < 0.001, respectively). The Korean version of the QDS showed a good significant correlation with functional scales of SF-36.
Conclusions: The adapted Korean version of the QDS was successfully translated and showed acceptable measurement properties, and as such, is considered suitable for outcome assessments in the Korean-speaking patients with low back pain.