The Modified Low Back Pain Disability Questionnaire: Reliability, Validity, and Responsiveness of a Dutch Language Version.

STUDY DESIGN: Cross-sectional study.

OBJECTIVE: The goal of this study is to translate the English version of the Modified Low Back Pain Disability Questionnaire (MDQ) into a Dutch version and investigate its clinimetric properties for patients with nonspecific chronic low back pain (CLBP).

SUMMARY OF BACKGROUND DATA: Fritz et al (2001) developed a modified version of the Oswestry Disability Questionnaire (ODI) to assess functional status and named it the MDQ. In this version, a question regarding employment and homemaking ability was substituted for the question related to sex life. Good clinimetric properties for the MDQ were identified but up until now it is not clear whether the clinimetric properties of the MDQ would change if it was translated into a Dutch version.

METHODS: Translation of the MDQ into Dutch was done in 4 steps. Test-retest reliability was investigated using the intraclass correlation coefficient (ICC) model. Validity was calculated using Pearson correlations and a 2-way analysis of variance for repeated measures. Finally, responsiveness was calculated with the area under the curve (AUC), minimal detectable change (MDC), and the standardized response mean (SRM).

RESULTS: A total of 80 completed questionnaires were collected in 3 different hospitals and a total of 43 patients finished a 9 weeks intervention period, completing the retest. Test-retest reliability was excellent with an ICC of 0.89 (95% confidence interval [CI], 0.74-0.95). To confirm the convergent validity, the MDQ answered all predefined hypothesises (r = -0.65-0.69/P = 0.01-0.00) and good results for construct validity were found (P = 0.02). The MDQ had an AUC of 0.64 (95% confidence interval [CI], 0.47-0.81), an MDC of 8.80 points, and a SRM of 0.65.

CONCLUSION: The Dutch version of the MDQ shows good clinimetric properties and is shown to be usable in the assessment of the functional status of Dutch-speaking patients with nonspecific CLBP.

LEVEL OF EVIDENCE: 3.