Objective: To undertake a comparative examination of the reliability and validity of two frequently used self-report measures of functional disability, the Pain Disability Index (PDI) and the Oswestry Low Back Pain Disability Questionnaire (OLBPDQ).
Design: A descriptive ex-post facto design was used in the study.
Setting: Pain clinics and neurosurgical units at three metropolitan hospitals. Subjects: One hundred patients with chronic low back pain of noncancer origin were administered the two questionnaires as part of a larger questionnaire battery.
Results: Acceptable internal consistency values of 0.76 for the PDI and 0.71 for the OLBPDQ were obtained. A correlation of r = 0.63 was found between the PDI and the OLBPDQ, supporting the concurrent validity of the two scales. Both the scales were found to be correlated to the Beck Depression Inventory scores (PDI, r = 0.42; OLBPDQ, r = 0.39), with higher disability associated with greater depression. Only the total PDI score was found to be sensitive to functional status differences within the patient sample.
Conclusions: These findings support other recent work in favor of the PDI. The PDI had a slightly higher internal consistency and was more sensitive than the OLBPDQ.