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.