A reliability and validity study of a translated, culturally adapted questionnaire.
The aims of the present study were to translate the Quebec Back Pain Disability Scale (QDS) into Turkish, to perform its cross-cultural adaptation for Turkish patients with LBP, and to investigate its validity and test-retest reliability.
As a widely used scale in the evaluation of patients with low back pain (LBP), the QDS awaits formal translation and validation into Turkish to achieve an equivalent questionnaire and to allow comparability of data.
The translation and cross-cultural adaptation of the original questionnaire were performed in accordance with published guidelines. Translation and retranslation of the English version of the QDS was performed blindly and independently by 4 different individuals, and adapted by a team. Hundred patients with LBP were included in our study. The physical examinations were evaluated and the Schober test was assessed for a mobility measurement of the spine. The patients were asked to complete a questionnaire booklet containing the Turkish versions of the modified Oswestry Disability Index (ODI) and QDS, and Visual Analog Scale (VAS) measure of pain. All assessments were repeated 24 hours later for all of the patients. Reliability was evaluated using internal consistency and the intraclass correlation coefficient (ICC). Concurrent validity was measured by comparing the Turkish version of the QDS results to VAS and the Schober test scores. Also, for construct validity, the results of the scale were compared with the Turkish version of modified ODI.
The QDS showed excellent test-retest reliability as evidenced by the high ICC for 2 test occasions (ICC = 0.9221, P < 0.000). Also, internal consistency was found to be adequate at both assessments with Cronbach's alpha (0.9405 and 0.9537 at day 0 and 1, respectively). There was a positive correlation between QDS and VAS both for day 0 (r = 0.368; P < 0.000) and for day 1 (r = 0.441; P < 0.000). There was no correlation determined in the comparison of the QDS sum scores with Schober testing for day 0; however, significant negative correlations in these parameters were observed for day 1 (r = -0.249 P = 0.014). Also significantly positive correlations were deter- mined between the Turkish version of the QDS and the Turkish version of the modified ODI for both day 0 and day 1 (r = 0.666, P < 0.000, r = 0.681; P < 0.000, respectively).
The results of our study show that QDS as a functional status questionnaire has been translated into Turkish without losing the psychometric properties of the original version. The Turkish version of the QDS has good comprehensibility, internal consistency, and validity and is an adequate and useful instrument for the evaluation of disability in patients with LBP.