Optimum trace count necessary for jitter calculation in single-fiber electromyography

Objective – To clarify the optimum trace count for jitter calculation. Materials and methods – Single‐fiber electromyography was performed during voluntary contraction (VC‐SFEMG) of extensor digitorum muscle in six healthy and five myasthenic subjects. Twenty single‐fiber action potential (SFAP) pairs were recorded from each subject. For each pair, 100 consecutive traces were recorded and stored for off‐line analysis. Ten different jitters were calculated in 10 consecutive steps for each SFAP pair by increasing the number of traces included to analysis (from 10 to 100). The jitter calculated in each step was compared with that calculated from 100 traces. Results – Sixty was the optimum number of trace count for both myasthenics and normal controls. Using less than 60 traces for jitter calculation revealed lower values. Conclusion – Jitter calculation should be performed from at least 60 traces in VC‐SFEMG. Less numbers yield lower jitter and may cause diagnostic error.