Evaluating the diagnostic utility of the flexion-compression test for carpal tunnel syndrome.

Background: We sought to determine the diagnostic utility of the flexion-compression (F-C) test for carpal tunnel syndrome (CTS). Using electrodiagnostic testing as the gold standard, we hypothesized that the F-C test would be a better diagnostic test for CTS as compared to the wrist flexion (Phalen's) or palmar compression (Durkan's) tests alone. Methods: We studied patients who presented with and without CTS symptoms, designated as study and control group patients, respectively. At the first clinic visit, all patients were evaluated using the CTS-6 score, and then the Phalen's, Durkan's, and F-C tests in a random order. Patients in the study group were then sent for electrodiagnostic testing. Results: 162 patients were included after power analysis, 81 each in the study and control groups. Among study group patients with electrodiagnostic evidence of CTS, the positive likelihood ratio (LR+) of the Phalen's test (1.29) was higher than the Durkan's (1.06) and F-C (0.95) tests, though less than the CTS-6 score (1.64). Performing any physical exam test in conjunction with the CTS-6 score was not more useful than the CTS-6 alone. As expected, all three physical exam maneuvers were more likely to be positive among study patients compared to control patients. Conclusions: None of the physical exam maneuvers were highly predictive of electrophysiologically-positive CTS. The CTS-6 score alone better predicts electrodiagnostic evidence of CTS than physical exam, though it only very slightly increases the post-test probability of disease. Formal electrodiagnostic testing remains important in diagnosing CTS when compared to physical exam maneuvers and CTS-6.