Comparison Of Sonography And Nerve Conduction Study In The Dtagnosis Of Carpal Tunnel Syndrome

ObjectiveTo determine the diagnostic value of sonography in the diagnosis of carpal tunnel syndrome and to investigate the benefit of using sonography together with nerve conduction study for the diagnosis of carpal tunnel syndrome, by comparing sonography with nerve conduction study using clinical diagnosis as the reference standard.MethodsForty-one wrists of 26 patients were enrolled, along with forty-four wrists of 28 controls whose age and gender were matched with the patients. All patients and controls had sonographic measurement of the cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet and at the carpal tunnel outlet and nerve conduction study. Compare the CSA of the median nerve between patients and controls. A receiver operating characteristic (ROC) curve was fitted to the sonographic measurements, using the clinical criteria as the reference standard, to determine the optimum cutoff point and to evaluate the diagnostic accuracy of sonographic measurements. Sensitivity and specificity were obtained and compared between sonography and nerve conduction study. The sensitivity and specificity of the combined tests were compared with those of nerve conduction study.ResultsThere were no significant differences in age, gender and body mass index between patients and controls (P>0.05). The CSA at the tunnel inlet was significantly larger in patients than in controls (P<0.01), while at the carpal tunnel outlet was similar in both groups (P=0.06). When the ROC curve was fitted for sonography using clinical criteria as the reference standard, the area under the curve was 0.73 (95% CI, 0.62~0.83) for the CSA at the carpal tunnel inlet and 0.61 (95% CI, 0.49~0.73) for the CSA at the carpal tunnel outlet. When the ROC curve was fitted for sonography using nerve conduction study results as the reference standard, the area under the curve was 0.84 (95% CI, 0.75~0.92). The best cutoff value of CSA at the tunnel inlet was 10.4mm2, which had a sensitivity of 76% and a specificity of 64%. Nerve conduction study showed a sensitivity of 80% and a specificity of 84%. Sensitivity was similar between sonography and nerve conduction study (P=0.59), whereas specificity was significantly lower in sonography than in nerve conduction study (P=0.03). Sensitivity and specificity of the series test of sonography and nerve conduction study have no significant changes with nerve conduction study (P=0.21 and 0.33, respectively). Specificity of the parallel test of sonography and nerve conduction study was significantly lowered (P=0.01) without significant change in sensitivity (P=0.36) with nerve conduction study.ConclusionsAlthough the sensitivity of sonography is similar to nerve conduction study for the diagnosis of carpal tunnel syndrome, its diagnostic accuracy is lower than nerve conduction study. Sonography was not complementary to nerve conduction study, and there was no added benefit of using sonography and nerve conduction study together with regard to diagnosis of carpal tunnel syndrome.