The sensitivity and specificity of tests for carpal tunnel syndrome vary with the comparison subjects.

The performance of a variety of common office-based clinical tests for detection of carpal tunnel syndrome (CTS) was assessed in 119 subjects with and without electrophysiological evidence of CTS. Symptoms compatible with CTS and electrophysiological tests positive for median mononeuropathy at the wrist were observed in 57 hands, symptoms compatible with CTS and normal electrophysiological test results were observed in 58 hands, and no symptoms compatible with CTS and normal electrophysiological test results were observed in 123 hands. For all the diagnostic tests studied, the proportion of subjects who had a false positive clinical test result was much higher in the electrophysiologically normal subjects who had CTS compatible hand symptoms than in the electrophysiologically normal subjects who were asymptomatic. These results suggest that many studies that have evaluated diagnostic tests for CTS have produced falsely optimistic estimates of the test's performance because of their use of asymptomatic comparison subjects.