Comparison of sonography and electrodiagnostic testing in the diagnosis of carpal tunnel syndrome.

PURPOSE: To determine whether sonography can be an alternative method to nerve conduction study (NCS) in the diagnosis of carpal tunnel syndrome (CTS), by comparing sonography with nerve conduction study using clinical diagnosis as the reference standard.

METHODS: Forty-one wrists of 29 patients were enrolled, along with the same number of age- and gender-matched controls. All patients had sonographic measurement of the cross-sectional area (CSA) of the median nerve and NCS. Sensitivity and specificity were obtained and compared between sonography and NCS.

RESULTS: There were no significant differences in age, gender, body mass index and involved side between patients and controls (p<.05). The CSA at the tunnel inlet was significantly larger in patients than in controls (p=.03). The best cutoff value of CSA at the tunnel inlet was 10.7 mm(2), which had a sensitivity of 66% and a specificity of 63%. NCS showed a sensitivity of 78% and a specificity of 83%. Sensitivity was similar between sonography and NCS (p=0.27), whereas specificity was significantly lower in sonography than in NCS (p=0.02).

CONCLUSIONS: Sonography is not accurate enough to replace NCS for the diagnosis of CTS.

TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic III.