Relationships between functional capacity measures and baseline psychological measures in chronic pain patients.

The extent to which baseline psychological measures, pain, and compensation status are related to admission and posttreatment functional capacity and employment outcome was investigated. Four pass/fail functional capacity tests based on the DOT (Dictionary of Occupational Titles) classification system and previously shown to be predictive of treatment outcome in chronic pain patients were analyzed in relation to baseline measures of depression, state and trait anxiety, and perceived stress. Statistical tests of all measures with employment level at admission to treatment, 1 month follow-up and at long-term follow-up were also performed. The results showed that pain level and/or compensation status were the primary predictors of functional capacity and employment status at follow-up. Admission functional capacity measures were also predictors of employment outcome. Depression scores at admission predicted some admission functional capacity results, however, psychological scores were not as significantly related to discharge functional capacity tests. One functional capacity test, the crouching test, was an independent predictor of short- and long-term employment outcome. Trait anxiety was the only psychological factor that was independently predictive of long-term employment outcome. In conclusion, these results suggest that psychological variables are related to measures of functional capacity measured at admission. However, psychological measures at admission are not good predictors of later functional capacity measures. Functional capacity measures are important predictors of follow-up employment outcome, but return to work cannot be predicted without taking pain into account.