Simultaneous bilateral hand strength testing in a client population, part I: diagnostic, observational and subjective complaint correlates to consistency of effort.

OBJECTIVES 1. To determine if scores on pain questionnaires and overt behaviors during a functional capacity evaluation (FCE) were related to variability between repeated measures during a hand strength assessment. 2. To determine if failure of statistically-based validity criteria, as proposed by Schapmire, St. James and Townsend et al. [26] is likely to be due to pain. PARTICIPANTS 200 consecutive clients presenting for an FCE. METHODS Subjects filled out pain questionnaires, were observed for various behaviors and were administered the distraction-based hand strength assessment. RESULTS Clients failing two or more of the statistically-based validity criteria had higher scores on most pain questionnaires, presented with a higher frequency of various pain behaviors (p < 0.05 and < 0.001, respectively), and had a lower rate of relevant surgeries (p < 0.001). There was no statistically significant difference in the number of failed validity criteria between this group of clients and for normal subjects feigning weakness in a controlled study (p> 0.05). CONCLUSIONS Pain does not reasonably explain the failure of the statistically-based validity criteria. The protocol is appropriate for use in a client population.