The sensitivity and specificity of functional capacity evaluations in determining maximal effort: a randomized trial.

Abstract

Randomized trial. To determine the sensitivity and specificity of maximal effort testing in functional capacity evaluations. Functional capacity evaluations are widely used to determine when an injured worker is able to return to work. The accurate assessment of function is dependent on a patient's willingness to exert maximal effort during evaluation. Although many tests are used to suggest the presence of maximal or submaximal effort, it is unclear whether these tests can actually do what they are hoped to do. Ninety study participants with low back pain were randomized into either a 100% effort group or a 60% effort group. After a thorough evaluation, the blinded tester was asked to give an overall opinion as to whether or not the participant was giving 100% effort or 60% effort. The tester's opinion on maximal effort tests within the functional capacity evaluation had an overall specificity of 84.1% and a sensitivity of 65.2%. Only 5 of 17 commonly used maximal effort tests were able to individually differentiate between maximal and submaximal effort. The final logistic regression model was able to find three covariates with reasonable explanation of the proportion of variance in the outcome variable of effort (R 3 0.444) with goodness of fit. The determination of maximal effort in a functional capacity evaluation is complex. Because of the wide-ranging medicolegal and ethical considerations, caution is recommended in the labeling of patients as exerting either maximal or submaximal effort.