Objective: This was a descriptive and exploratory study. The purpose was to determine reliability and clinical reference values computed with approriate statistical methods for electrophysiologic measures of ulnar sensory nerve function using data from healthy subjects obtained with the recommended elbow testing position. Methods: Antidromic sensory nerve conduction studies of the ulnar nerve using surface electrodes were performed on 100 disease free volunteers. Sensory nerve evoked potentials were elicited from stimulation at the wrist, below-elbow, and above-elbow sites in all subjects. Sensory distal latency (SDL) and sensory nerve conduction velocity (SNCV) were calculated to both the onset and to the peak of the evoked potentials; sensory nerve action potential (SNAP) amplitude was measured from onset to negative peak of the evoked potential. Thirty subjects were tested a second time to collect data for intrarater reliability analyses. Multiple linear regression models were constructed to examine the use of age, body mass index, gender, and finger girth to predict forearm and across-elbow SNCV and SNAP amplitude. Results: Responses were obtained from all subjects. Intraclass correlation coefficients were greater than 0.85 for all paired measures of SDL, SNCV, and SNAP amplitude. Reference values were computed from data optimally transformed to minimize skew. Reference values were: SDL measured to onset and peak 2.34 msec and 3.11 msec; forearm SNCV measured to onset and peak 54 m/sec and 53 m/sec; across-elbow SNCV measured to onset and peak 47 m/sec and 5 m/sec; SNAP amplitude from wrist, below elbow, and above elbow stimulation 10.79uV, 4.66uV, and 3.33uV respectively; SNAP amplitude decrement across the elbow 46%. No independent variable accounted for more than 5% of the variance in across-elbow SNCV; finger girth accounted for approximately 28% of the variance in above-elbow SNAP amplitude. Conclusion: Ulnar SDL, SNCV, and SNAP amplitude are reliable measures. Reference values for SNCV and SNAP amplitude were computed using recommended statistical methods and elbow position. No strong statistical models for prediction of SNCV or SNAP amplitude could be derived from the limited set of predictor variables. The reliability analyses in the current study, combined with relatively low level of measurement error, suggest that these ulnar sensory reference values computed using the recommended elbow position and appropriate statistical methodology may be used with confidence.
