Diagnostic Accuracy of Ultrasound Parameters in Carpal Tunnel Syndrome: Additional Criteria for Diagnosis.

OBJECTIVES

To determine the diagnostic capacity of ultrasound (US) in detecting carpal tunnel syndrome (CTS).

METHODS

Volunteer adults with and without CTS symptoms were recruited from offices in metropolitan Manila, where employees' work was hand/wrist intensive. Carpal tunnel syndrome was independently diagnosed by a reference standard (positive findings on a physical examination and nerve conduction studies). Blinded US measurements were taken of the median nerve (cross-sectional area, hypervascularity, wrist-to-forearm ratio, wrist-forearm difference, swelling ratio, flattening ratio, and palmar bowing of the flexor retinaculum) at the carpal tunnel inlet and carpal tunnel outlet (CTO).

RESULTS

A total of 117 eligible consenting participants (234 hands) were included, with 54 hands (23.1%) with a diagnosis of CTS. There were no anthropometric differences between arms with and without CTS. Men and women older than 33 years were 5 times more likely to report CTS than younger people. A CTO wrist-forearm difference of greater than 0.03 cm had the strongest association with CTS (odds ratio, 4.7; 95% confidence interval, 1.4-15.9), with an area under the curve of 0.58 (sensitivity, 94.4%; specificity, 21.7%). The area under the curve increased to 0.59 when the next strongest measurement (CTO hypervascularity of 1+: odds ratio, 3.8; 95% confidence interval, 1.8-8.1) was included (sensitivity, 98.1%; specificity, 27.7%). Adding further US parameters did not improve the diagnostic capacity of US for CTS. Diagnostic capacity was independent of age and the duration of CTS symptoms.

CONCLUSIONS

Combining US findings for the CTO wrist-forearm difference and hypervascularity provides a sensitive, alternative diagnostic tool for CTS.