The interrater reliability of a functional capacity evaluation: the physical work performance evaluation.

The purpose was to evaluate the interrater reliability of the Dynamic Strength, Position Tolerance, and Mobility tasks of the Physical Work Performance Evaluation (PWPE), a Functional Capacity Evaluation often used with workers disabled due to back pain. For each worker's evaluation, two raters were preselected among five trained raters. One of the raters administered the PWPE while the other functioned as a silent rater. A convenience sample of 40 workers disabled due to back pain and referred to an occupational rehabilitation center was used. In general, the reliability was "substantial" (0.61 < or = kappa < or = 0.80) to "almost perfect" (0.81 < or = kappa < or = 1.00) for most of the 21 tasks and three sections of the PWPE evaluated with the exception of three tasks in the Mobility section (ladder climbing (kappa = 0.47), repetitive trunk rotation--standing (kappa = 0.54), and repetitive trunk rotation--sitting (kappa = 0.37)) task and the Mobility section itself (kappa = 0.54). Several reasons could explain the lower agreement on the observation of the physical signs associated with these tasks. Since these tasks involve rotation movements or complex neuromuscular integration, it seemed difficult for the raters to define what are the normal physical signs and when physical signs of maximal functional capacity are present. The criteria for establishing the presence of the physical signs in the PWPE should be improved.