Frischer T, Meinert R, Urbanek R, Kuehr J
University Children's Hospital, Vienna, Austria.
Thorax. 1995 Jan;50(1):35-9. doi: 10.1136/thx.50.1.35.
Variability of peak expiratory flow (PEF) has been proposed as a surrogate for bronchial hyperresponsiveness. The normal range of variability of PEF for children has been reported and the test has been used to screen for asthma in population based studies. However, there is little information on the reproducibility of the method in epidemiological settings.
In a cohort study of primary school children the variability in PEF was recorded in two consecutive years for one week (first survey) and two weeks (second survey) using mini Wright peak flow meters. PEF was recorded twice daily (morning and evening) and average amplitude as a percentage of mean was calculated as a standard measure of PEF variability for each single week of PEF measurement. Children with PEF variability exceeding the 90% percentile of the distribution for the specific time period were regarded as having increased variability of PEF.
Of 66 children with increased PEF variability in the first year, 13 (19.7%) had an abnormal test in the first week of the second year. Of 543 children with normal PEF variability in the first year, 44 (8.1%) had an abnormal test in the second study year (odds ratio 2.8, confidence interval (CI) 1.4 to 5.4). Of 646 children in the second survey 61 (9.4%) were abnormal during the first week and 68 (10.5%) had an increased PEF variability during the second week, but only 24 (3.7%) children had an increased PEF variability in both weeks. The sensitivity (specificity) for doctor-diagnosed asthma (12 month period prevalence) was 36.4% (91.0%) in the first week of the second survey. When measurements of both weeks of the second survey were used to calculate PEF variability there was little improvement in the sensitivity (38.1%) and specificity (91.5%), mainly because of decreased compliance in the second measurement week.
In young children assessment of PEF variability in order to screen for asthma is of limited value because of the low reproducibility of the method.
呼气峰值流速（PEF）的变异性已被提议作为支气管高反应性的替代指标。儿童PEF变异性的正常范围已有报道，该测试已用于基于人群的哮喘筛查研究。然而，关于该方法在流行病学环境中的可重复性信息很少。
在一项对小学生的队列研究中，使用小型赖特峰值流量计连续两年记录PEF变异性，第一年记录一周（第一次调查），第二年记录两周（第二次调查）。每天记录两次PEF（早晨和晚上），并计算平均幅度占平均值的百分比，作为每次PEF测量单周PEF变异性的标准指标。PEF变异性超过特定时间段分布第90百分位数的儿童被视为PEF变异性增加。
在第一年PEF变异性增加的66名儿童中，13名（19.7%）在第二年第一周测试异常。在第一年PEF变异性正常的543名儿童中，44名（8.1%）在第二年研究中测试异常（比值比2.8，置信区间（CI）1.4至5.4）。在第二次调查的646名儿童中，61名（9.4%）在第一周异常，68名（10.5%）在第二周PEF变异性增加，但只有24名（3.7%）儿童在两周内PEF变异性均增加。第二次调查第一周医生诊断哮喘（12个月患病率）的敏感性（特异性）为36.4%（91.0%）。当使用第二次调查两周的测量值来计算PEF变异性时，敏感性（38.1%）和特异性（91.5%）几乎没有改善，主要是因为第二测量周的依从性降低。
由于该方法的可重复性低，在幼儿中评估PEF变异性以筛查哮喘的价值有限。
