Validity of current electrodiagnostic techniques in the diagnosis of carpal tunnel syndrome

BACKGROUND Determining the validity of current median sensory nerve conduction techniques for diagnosis of carpal tunnel syndrome (CTS). METHODS Eighty five patients with clinical diagnosis of CTS were compared with the same number of healthy people. The validity of electrodiagnostic tests were compared in a case-control manner. These electrodiagnostic techniques included long-segment, short-segment, 2-segment and relative slowing studies; as well as distoproximal ratio. Receiver Operating Characteristic (ROC) curve employed for comparison, determining the optimal cut-off points for each test. Validity was evaluated with likelihood ratio. RESULTS Likelihood ratio (LHR) for Radial-median sensory latency difference was ∞, while LHR for ulnarmedian sensory latency difference was 16.9. Sensitivity of Two-segment method was 98.8% and mixed palmwrist median Nerve Conduction Velocity (NCV) study showed a sensitivity and specificity of 97.6%, 83.5% respectively. CONCLUSIONS Radial-median latency difference study (optimal cut-off point ≥0.5) and study of wrist-segment NCV (optimal cut-off point <50.45) were the most valuable techniques in diagnosis of CTS, respectively. Median-ulnar latency difference study and disto-proximal ratio study had more diagnostic implication than long and short (mixed) segment technique in this regard.