OBJECTIVE: To evaluate the accuracy of inlet and outlet ultrasonography measurements for the diagnosis of carpal tunnel syndrome (CTS).
DATA SOURCES: MEDLINE, EMBASE, the Cochrane Library, and the Web of Science databases were systematically searched from inception to February 2017.
STUDY SELECTION: Observational studies comparing the diagnostic accuracy of inlet and outlet ultrasonography measurements were selected.
DATA EXTRACTION: Random-effects models for the diagnostic odds ratio (dOR) values computed by Moses' constant for a linear model and 95% confidence intervals (CIs) were used to calculate the accuracy of the test. Hierarchical summary receiver operating characteristic curves were used to summarize overall test performance.
DATA SYNTHESIS: Twenty-eight published studies were included in the meta-analysis. The pooled dOR values for the diagnosis of CTS were 31.11 (95% CI, 20.42-47.40) for inlet-level and 16.94 (95% CI, 7.58-37.86) for outlet-level measurements. The 95% confidence region for the point that summarizes overall test performance of the included studies occurred where the cutoffs ranged from 9.0 to 12.6mm2for inlet-level measurements and from 9.5 to 10.0mm2for outlet-level measurements.
CONCLUSIONS: Both ultrasonography measurements for the diagnosis of CTS showed sufficient accuracy for their use in clinical settings, although the overall accuracy was slightly higher for inlet-level than for outlet-level measurements. The addition of outlet and inlet measurements does not increase the accuracy for the diagnosis. Therefore, the inlet-level ultrasonography measurement appears to be an appropriate method for the diagnosis of CTS.
The final conclusion of "it is known that there is substantial variability in the normal size of the median nerve; consequently, providing a cutoff threshold of median nerve cross-sectional area as a diagnostic criterion could be rather hazardous" seems to negate use of this method.
Physicians specializing in CTS diagnosis already know that some studies show that ultrasonograpy may provide information about the area of the median nerve at wrist. However, all the studies reviewed are cross-sectional, whereas EMG has been extensively tested longitudinally in the diagnosis of CTS.