Engstrom J W, Olney R K
Department of Neurology, School of Medicine, University of California, San Francisco 94143-0114.
Muscle Nerve. 1992 Mar;15(3):277-81. doi: 10.1002/mus.880150304.
This study of quantitative electromyography examines the influence of sample size on motor unit action potential (MUAP) tolerance limits, intertrial variability, and diagnostic sensitivity. We recorded 20 randomly selected MUAPs from the biceps muscle twice in 21 normal subjects, and once in 10 patients with myopathy. The 95% tolerance limits for mean total duration in normal subjects progressively narrowed from 6.6 to 14.2 ms for 5 MUAPs to 7.4 to 13.0 ms for 20 MUAPs. The 95% tolerance limits for intertrial variability were +/-22% for mean total duration of 20 MUAPs. Larger sample size had a greater effect on reducing intertrial variability than on narrowing 95% tolerance limits for amplitude and area. Quantitative EMG results for duration supported the presence of myopathy in 2 of 10 patients with analysis of 5 MUAPs, and 9 patients with analysis of 20 MUAPs. Although analysis of 5 potentials may be adequate for diagnosis occasionally, quantitative analysis of 20 MUAPs narrows tolerance limits, reduces intertrial variability, and improves diagnostic sensitivity.
这项定量肌电图研究考察了样本量对运动单位动作电位（MUAP）耐受限度、试验间变异性和诊断敏感性的影响。我们在21名正常受试者中，从肱二头肌随机选取20个MUAP记录两次，在10名肌病患者中记录一次。正常受试者平均总时限的95%耐受限度，对于5个MUAP，从6.6至14.2毫秒逐渐缩小至对于20个MUAP的7.4至13.0毫秒。对于20个MUAP平均总时限，试验间变异性的95%耐受限度为±22%。更大的样本量对降低试验间变异性的影响，比对缩小幅度和面积的95%耐受限度的影响更大。对持续时间的定量肌电图结果，在分析5个MUAP时支持10名患者中有2名存在肌病，在分析20个MUAP时支持9名患者存在肌病。虽然偶尔分析5个电位可能足以进行诊断，但对20个MUAP进行定量分析可缩小耐受限度、降低试验间变异性并提高诊断敏感性。
