"Movement" in work status after pain facility treatment.

Study Design: This was a randomized prospective follow-up study of pain facility treatment of chronic pain patients with low back pain, with return to work and work capacity as the outcome measures.

Objectives: To determine if after pain facility treatment chronic pain patients "move" in and out of work and in their work capacity; to determine the patterns of "movement;" and to determine the post-pain facility treatment follow-up sampling time points that would maximize the number of chronic pain patients correctly classified according to their final work and work capacity status.

Summary Of Background Data: Past research and empiric observation have indicated that chronic pain patients may "move" after pain facility treatment in and out of work and in their job work capacity. Such "movement" can affect the results of outcome studies.

Methods: Two hundred thirty-six consecutive chronic pain patients who fit study selection criteria were followed up at 1, 3, 6, 12, 18, 24, and 30 months after pain facility treatment for determination of work and work capacity status and separated according to the pattern of movement. Stepwise discriminant analysis was used to answer the study objectives. "Movement" in and out of work for these chronic pain patients also was compared with the US general population.

Results: Chronic pain patients demonstrated eight work and four work capacity movement patterns. The 24- and 1-month time points predicted final work status correctly for 97.0% and 77.0% of the chronic pain patients, respectively, whereas the most significant predictor for correct work capacity status was the 24-month point. The annual percentage change in employment status for these chronic pain patients was more than in the US general population.

Conclusions: Because chronic pain patients "move" in and out of employment and for work capacity status after pain facility treatment, future outcome studies using these measures will have to consider carefully the impact of "movement" on their results.