INTERCORRELATION AND TEST-RETEST RELIABILITY OF THE PAIN DISABILITY INDEX (PDI) AND THE OSWESTRY DISABILITY QUESTIONNAIRE (ODQ) AND THEIR CORRELATION WITH PAIN INTENSITY IN LOW-BACK-PAIN PATIENTS

Objective: To determine the intercorrelation between subjective disabi lity, as assessed with the Pain Disability Index (PDI) and the Oswestr y Disability Questionnaire (ODQ) and their correlation with visual ana logue scale (VAS) pain intensity ratings. Design and Subjects: Questio nnaires were administered to 94 patients with chronic low back pain wi th or without radiation into the legs of at least 3 months' duration. Setting: Tertiary care center. Results: High correlations were noted b etween the ODQ and PDI (r = 0.83) and PDI factor 1 (r = 0.84), a subsc ale of the PDI. Lower correlations were noted between pain intensity ( VAS) scores and the ODQ (r = 0.62) and the PDI (r = 0.69). A weaker co rrelation (r = 0.41) was noted between the ODQ and PDI factor 2. Intra class correlation coefficients (ICC) for test-retest reliability in 20 patients (time interval 1 week) were for the ODQ ICC = 0.83, PDI ICC = 0.91, PDI percentage score ICC = 0.91, PDI factor 1 ICC = 0.87, and PDI factor 2 ICC = 0.73, respectively. Conclusions. The present result s suggest that either the PDI or the percentage score PDI and also the even shorter-to-administer PDI factor 1 may be useful and reliable te sts for the assessment of subjective disability in low back pain patie nts. As noted by the moderate intercorrelations with pain intensity sc ores, both the PDI and the ODQ address a broader concept of disability than that directly related to pain intensity.