The diagnostic accuracy of high-resolution ultrasound in screening for carpal tunnel syndrome and grading its severity is moderated by age.

OBJECTIVE

To assess the effect of age on the accuracy of high-resolution ultrasound (HRUS) in the diagnosis and grading of carpal tunnel syndrome (CTS).

METHODS

Patients with symptoms and signs of CTS (N = 527 wrists) were evaluated using electrodiagnostic studies (EDx) for CTS diagnosis and grading. Median nerve cross-sectional areas at carpal tunnel inlet (CSA) and at forearm level were measured by HRUS and the ratio of these values was calculated (WFR). Healthy controls underwent identical testing (N = 122 wrists). HRUS accuracy was assessed against the EDx standard by Receiver Operator Characteristic (ROC) curve analysis.

RESULTS

In patients >65 y with moderate and severe CTS, disease-related increases in CSA and WFR were negatively correlated with increasing age. Subjects were grouped by age into younger (<65 y) and older (≥65 y). The c-statistics for CSA and WFR respectively were: For CTS diagnosis, younger group: 0.94 and 0.96 (excellent); older group: 0.85 and 0.86 (satisfactory). For CTS grading, younger group: differentiating mild CTS from controls: 0.90 and 0.92 (excellent); mild from moderate: 0.79 and 0.74 (satisfactory); moderate from severe: 0.82 and 0.78 (satisfactory). For CTS grading, older group: differentiating mild CTS from controls: 0.83 and 0.83 (satisfactory); mild from moderate: 0.53 and 0.61 (poor); moderate from severe: 0.65 and 0.53 (poor).

CONCLUSIONS

For subjects aged <65 y, HRUS accuracy is excellent in CTS diagnosis and satisfactory in grading. For older subjects, accuracy is satisfactory in diagnosis but not in grading.

SIGNIFICANCE: HRUS for CTS has diagnostic limitations selectively in older individuals.