The Oswestry Disability Index (version 2.1a): validation of a Dutch language version.

STUDY DESIGN: A cross-sectional study on baseline data.

OBJECTIVE: To translate the Oswestry Disability Index (ODI) version 2.1a into the Dutch language and to validate its use in a cohort of patients with chronic low back pain in secondary spine care.

SUMMARY OF BACKGROUND DATA: Patient-reported outcome measures (PROMs) are commonly accepted to evaluate the outcome of spine interventions. Functional status is an important outcome in spine research. The ODI is a recommended condition-specific patient-reported outcome measure used to evaluate functional status in patients with back pain. As yet, no formal translated Dutch version exists.

METHODS: The ODI was translated according to established guidelines. The final version was built into the electronic web-based system in addition with the Roland Morris Disability Questionnaire, the numeric rating scale for pain severity, 36-Item Short Form Health Survey Questionnaire for quality of life, and the hospital anxiety and depression scale. Baseline data were used of 244 patients with chronic low back pain who participated in a combined physical and psychological program. Floor and ceiling effects, internal consistency, and the construct validity were evaluated using quality criteria.

RESULTS: The mean ODI (standard deviation) was 39.6 (12.3); minimum 6, maximum 70. Most of the participants (88%) were moderately to severely disabled. Factor analysis determined a 1-factor structure (36% explained variance) and the homogeneity of ODI items is shown (Cronbach α = 0.79). The construct validity is supported as all (6:6) the a priori hypotheses were confirmed. Moreover, the ODI and Roland Morris Disability Questionnaire, showed a strong significant correlation (r = 0.68, P < 0.001) and an overlap: mean difference of -18 (95% limits of agreement: -44 to 8).

CONCLUSION: The Dutch ODI version 2.1a is a valid and valuable tool for the measurement of functional status and disability among Dutch patients with chronic low back pain. This translated condition-specific patient-reported outcome measure version is recommended for use in future back pain research and to evaluate outcome of back care in the Netherlands.