Is work status of low back pain patients best described by an automated device or by a questionnaire?

STUDY DESIGN A prospective cohort study of patients with subacute occupational back pain. OBJECTIVES To study the relation between a marketed opto-electric device measuring trunk kinematics, a widely used specific functional capacity questionnaire, and work status in back pain patients, and to assess the responsiveness to change in work status of the opto-electric device and the questionnaire. SUMMARY OF BACKGROUND DATA Several instruments have been developed to evaluate the functional capacities of patients with back pain, but the relation between these instruments and work status has rarely been studied. METHODS The relation between the opto-electric device, the questionnaire, and work status in patients with back pain was evaluated. The study population was a prospective cohort of patients with subacute back pain who were absent from regular work for more than 4 weeks. All data were compiled blindly on the same day, at study entry (4 weeks after work accident), and at 12, 24, and 52 weeks after the work accident. The validity of the questionnaire and opto-electric device scores was assessed with partial correlation analyses, standardized response mean, logistic regression analyses, and receiver operating characteristics curves. RESULTS The correlation between the questionnaire and opto-electric device scores was low. The questionnaire scores were significantly related to work status, but the opto-electric device scores were not. The questionnaire was responsive to change in work status, whereas the opto-electric device was not. CONCLUSIONS The opto-electric device scores were not related to either functional capacity scores (questionnaire) or work status in patients with low back pain, and the opto-electric device was not responsive to change in work status. Conversely, the questionnaire was related to work status and was responsive to change in work status.