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

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. 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. 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. 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.