Translation, adaptation and validation of the Moroccan version of the Quebec Back Pain Disability Scale

This study aims to translate and cross-culturally adapt the Moroccan version of the Quebec Back Pain Disability Scale (QDS) and to investigate its reliability and validity in Moroccan patients with low back pain (LBP). The translation and cross-cultural adaptation of the QDS were developed in agreement with published guidelines. The QDS was translated by use of the forward and backward translation procedure. After pretest, it was validated in 64 Moroccan patients with LBP. The QDS was recorded twice, at baseline visit and 72 h later. Reproducibility was evaluated using intraclass correlation coefficient (ICC) and Bland and Altman method. Internal consistency was measured by Cronbach alpha coefficient. Ceiling and floor effects were assessed. Validity was measured by correlating the scores of the Moroccan QDS with visual analogue scale (VAS) for Pain, Disability VAS, Schober test, fingertip-floor measurement and the Moroccan version of the Roland Morris Disability Questionnaire (RMDQ) by means of the Spearman rank correlation coefficient. Association with gender and education level was also studied. Reliability was excellent with an ICC (type 2.1) of 0.959 (CI 95%: 0.934-0.975). The internal consistency was high with a Cronbach alpha of 0.979. The Bland and Altman method showed homogenous distribution of the differences, with no systematic trend. There were no floor or ceiling effects. The correlation between QDS and RMDQ was very good (r=0.664; p <= 0.001). There was no correlation between QDS and the other variables. Accordingly, the Moroccan version of QDS has good reproducibility, internal consistency and validity for the assessment of disability in Moroccan-speaking patients with LBP.