We developed a modified Phalen's test (MPT), which uses sensory testing in Phalen's position, as a diagnostic screening tool for carpal tunnel syndrome (CTS). This study was designed to determine the sensitivity, specificity, and receiver operating characteristic (ROC) curve of the MPT for diagnosis of CTS.
Electrodiagnostic nerve conduction studies (EDS) were used as the gold standard. MPT was performed by a blinded examiner on patients prior to EDS. MPT was recorded as either positive or negative based on the presence or absence of a median nerve sensory deficit while the hand was in Phalen's position.
Sixty-six hands were included in this study. Chi-square for the MPT compared to EDS as the gold standard was 41.449 (P < 0.001), and the validity coefficient (phi) was 0.792 (P < 0.01). The traditional Phalen's test (TPT) compared to the EDS demonstrated a chi-square of 15.349 (P < 0.001) and a phi coefficient of 0.482 (P < 0.01). ROC curve estimates for the MPT revealed a sensitivity of 84.4% compared to 50% for the TPT. The standard error of the estimate for sensitivity was 3.3% for the MPT and 5.8% for the TPT.
The MPT is a highly useful screening diagnostic tool for CTS. The MPT demonstrates greater accuracy than the TPT for predicting CTS. The MPT also demonstrates greater sensitivity than the TPT in predicting a positive electrodiagnostic test for CTS.