Carpal tunnel sonography by the rheumatologist versus nerve conduction study by the neurologist.

OBJECTIVE

To determine the value of sonography (SG) performed by the rheumatologist to diagnose carpal tunnel syndrome (CTS).

METHODS

Sixty-three patients with clinical signs of CTS according to the neurologist, based on patient history and clinical examination, were studied. In the 6 weeks prior to surgery, SG was performed by a rheumatologist and nerve conduction study (NCS) was assessed. Improvement of initial complaints of 90% or more 3 months after surgery was considered to be the post-hoc gold standard for the diagnosis of CTS.

RESULTS

After surgery, 47 patients (75%) experienced > or = 90% relief of complaints. Mean cross sectional area of the median nerve for patients with CTS was 11.3 mm2 compared to 6.1 mm2 in the control group. The sensitivity to detect CTS was 0.70 for SG and 0.98 for NCS, and specificity was 0.63 for SG and 0.19 for NCS. Positive predictive value was 0.85 for SG and 0.78 for NCS; negative predictive value was 0.42 for SG and 0.75 for NCS. Accuracy was 0.68 for SG and 0.78 for NCS.

CONCLUSION

CTS can be identified by SG less sensitively but more specifically than by NCS.