Purpose
The purpose of the study was to determine the rate of false positives for nerve conduction
studies (NCSs) and ultrasound (US) in a population without signs and symptoms of carpal
tunnel syndrome (CTS) using a CTS-6 score of 0 as the reference standard.
Methods
Patients were included in this study if they were referred for NCSs for a reason other
than CTS (cubital tunnel syndrome and/or cervical radiculopathy) and they had a CTS-6
score of 0. An US measurement of the cross-sectional area (CSA) of the median nerve
at the level of the carpal tunnel inlet was performed by a certified ultrasound technician.
An a priori CSA cutoff of 10 mm2 or greater measured using US at the carpal tunnel inlet qualified as a positive diagnosis.
The NCSs were performed and interpreted according to national standards by a certified
electrodiagnostician. All patients in this study were considered to not have a diagnosis
of CTS based on the CTS-6 of 0.
Results
Forty hands with a CTS-6 of 0 were included in this study. The US was positive in
9 of 40(23%) and NCS was positive in 17 of 40 (43%). There were only 2 patients with
a false-positive US that did not also have a positive NCS. However, there were 11
patients who had a false-positive NCS that did not have a positive US.
Conclusions
This prospective cohort series has demonstrated that US has a lower false-positive
rate than NCSs in asymptomatic patients as measured by the CTS-6 diagnostic tool.
Studies with a low false-positive rate are preferred when ordering a confirmatory
diagnostic test. Therefore, if a confirmatory diagnostic test is desired, we recommend
that US be used rather than NCSs.
Type of study/level of evidence
Diagnostic II.
Key words
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Crasto JA, Scott ME, Fowler JR. Ultrasound measurement of the cross-sectional area of the median nerve: the effect of teaching on measurement accuracy [published online ahead of print September 1, 2017]. Hand (N Y). https://doi.org/10.1177/1558944717731857.
Article info
Publication history
Published online: January 09, 2019
Accepted:
November 20,
2018
Received:
April 29,
2018
Footnotes
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Identification
Copyright
© 2019 by the American Society for Surgery of the Hand. All rights reserved.
