[Validity and usefulness of echography in the carpal tunnel syndrome]

To evaluate the accuracy and utility of ultrasonography for the diagnosis of carpal tunnel syndrome (CTS).

Prospective and blind study of 75 wrists in 42 consecutive patients with suspected CTS. Electrodiagnostic testing (EDT) was used as gold standard. We measure different ultrasonographic parameters and based on a fitted receiver operating characteristic curve, we estimated post-test probabilities for the proximal, middle and distal cross-sectional area of median nerve. We analyzed interobserver and interreader reliability by 3 different explorers and 2 different readers, cost and the patient discomfort.

Mean ultrasound measurements were significantly higher in the EDT positive group. There was a high concordance between sonography and nerve conduction. A cut-off of 9.5 mm(2) resulted in the correct classification of 83% of cases (sensitivity 88% and specificity 67%). Conversely, a cut-off of >14 mm(2) or <7 mm(2) had excellent power to rule in CTS, with a post-test probability of 100% of specificity and sensitivity respectively. The interobserver acquisition ICC was 0.915-0.980, and the inter-reader ICC was 0.912-0.987. Ultrasound cost savings in this study were €J3217.59 (€42.9 per symptomatic wrist) and the discomfort perceived by the patient was significantly lesser 6.3 vs 56 in EDT (P <.0005).

Ultrasound median nerve crosssectional area is reliable and may be used to accurately rule in or rule out CTS. Sonography as a first-line test is cost-effective and is more satisfactory to the patients.