Sensitivity, specificity, and variability of nerve conduction velocity measurements in carpal tunnel syndrome.

Objective: To explore the diagnostic values of 8 commonly used electrodiagnostic techniques for measuring median nerve conduction velocity (NCV) in carpal tunnel syndrome (CTS).

Design: Sensitivity and specificity analyses.

Setting: A hospital-based electrodiagnostic laboratory.

Participants: Forty-four normal hands and 136 symptomatic hands.

Interventions: Not applicable.

Main Outcome Measures: (1) Long-segment studies: antidromic wrist-to-digit sensory NCV without subtraction, (2) short-segment studies: transcarpal palm-to-wrist mixed NCV without subtraction, and (3) 2 segment studies: antidromic transcarpal sensory NCV with subtraction (differential calculation from wrist-to-digit and palm-to-digit segments). Both onset and peak latency values were obtained for calculating the NCV. Sensitivity, specificity, and coefficient of variance were calculated for each NCV study.

Results: The short-segment, onset latency-based transcarpal mixed NCV yielded the highest sensitivity (75%).

Conclusions: Results from measurement of a single, short-nerve segment tended to be superior to results obtained by either long-segment studies or differential subtraction between 2 segments of the same nerve in the electrodiagnosis of CTS. Explanations for our results are offered from both electrophysiologic and statistical perspectives.