Psychometric properties and cross-cultural adaptation of the Brazilian Quebec back pain disability scale questionnaire.

STUDY DESIGN: Cross-cultural translation and psychometric testing.

OBJECTIVE: To translate and cross-culturally adapt the Quebec Back Pain Disability Scale (QDS) to Brazilian Portuguese and to examine its validity and reliability.

SUMMARY OF BACKGROUND DATA: Current literature shows the need to adopt reliable and internationally standardized methods for the analysis of low back pain. To our knowledge, this specific questionnaire has not been translated and validated for Portuguese-speaking patients.

METHODS: The translation and cross-cultural adaptation of the QDS were developed in agreement with internationally recommended methodology, and the resulting product was evaluated in this study with 54 consecutive patients. Internal consistency was obtained through Cronbach's alpha; reliability was estimated through the intraclass correlation coefficient and the Bland and Altman agreement (d = mean difference). Validity was determined by correlating the scores of the Brazil-QDS with the Brazilian version of the Roland-Morris Questionnaire and Visual Analogue Pain Scale by means of the Spearman rank correlation coefficient.

RESULTS: The internal consistency obtained was excellent (Cronbach's alpha = 0.97). Intraobserver and interobserver reliability were considered strong (ICC = 0.93-d = 0.68 and 0.96-d = 0.57, respectively). The correlation with Brazilian Roland-Morris Questionnaire and with the Visual Analogue Scale was high (r = 0.857; r = 0.758, respectively).

CONCLUSION: The data showed that the process of translation and cross-cultural adaptation were successful and that the adapted instrument demonstrated excellent psychometric properties.