Sawyer G, Miles J, Lewis S, Fitzharris P, Pearce N, Beasley R
Department of Medicine, Wellington School of Medicine, New Zealand.
Clin Exp Allergy. 1998 Dec;28(12):1565-70. doi: 10.1046/j.1365-2222.1998.00451.x.
International guidelines recommend that, in addition to symptoms and medication requirements, measurements of forced expiratory volume in one second (FEV1) and peak expiratory flow (PEF) are necessary for the objective assessment of asthma severity. The guidelines suggest that parity exists between measurements of FEV1 and PEF when expressed as percentage of predicted normal values, and that asthma severity can be classified as mild, moderate or severe on the basis of FEV and PEF measurements of > 80%, 60-80% and < 60% of predicted values, respectively.
To determine the relationship between measurements of FEV1 and PEF when expressed as percentage predicted values.
A total of 1198 paired measurements of FEV1 and PEF were obtained from the medical records of a random sample of 25 adult asthmatic patients attending a hospital-based chest clinic. Measurements of lung function were expressed as a percentage of predicted normal values, using the European Respiratory Society prediction equations for PEF and FEV1. For the individual paired measurements, the mean differences between PEF and FEV percentage predicted were calculated. Measurements of lung function were used to determine asthma severity with <60%, 60-80%, and >80% predicted FEV1 and PEF values representing severe, moderate and mild asthma, respectively. The proportion of paired measurements in which differences in classification resulted from the use of FEV1 or PEF percentage predicted values was then calculated.
In asthma of differing severity, there was considerable variability between measurements of FEV1 and PEF when expressed as percentage predicted values; calculation of the FEV1% predicted resulted in lower values than those of the PEF percentage predicted, with a mean difference of -17.2% (95% CI -16.3%, -18.1%). There was agreement in classification of asthma severity in only 49.9% (598/1198) of paired measurements. Different prediction equations, while variably altering the degree of misclassification, did not correct the basic differences in the assessment of asthma severity dependent on the use of FEV or PEF.
FEV1 and PEF values, expressed as percentage predicted, are not equivalent. Pending further evaluation, the authors suggest that published asthma guidelines should avoid the assumption of parity between these two measurements.
国际指南建议，除症状和药物需求外，一秒用力呼气量（FEV1）和呼气峰值流速（PEF）的测量对于客观评估哮喘严重程度是必要的。指南表明，当以预测正常值的百分比表示时，FEV1和PEF的测量结果相当，并且哮喘严重程度可根据FEV1和PEF测量值分别高于、介于和低于预测值的80%、60 - 80%和60%，分为轻度、中度或重度。
确定以预测值百分比表示时FEV1和PEF测量值之间的关系。
从一家医院胸科门诊的25例成年哮喘患者的随机样本病历中，共获取了1198对FEV1和PEF测量值。使用欧洲呼吸学会的PEF和FEV1预测方程，将肺功能测量值表示为预测正常值的百分比。对于每对测量值，计算PEF和FEV预测百分比之间的平均差异。使用肺功能测量值确定哮喘严重程度，FEV1和PEF预测值低于、介于和高于60%分别代表重度、中度和轻度哮喘。然后计算因使用FEV1或PEF预测百分比值而导致分类差异的测量值对的比例。
在不同严重程度的哮喘中，当以预测值百分比表示时，FEV1和PEF的测量值之间存在相当大的变异性；计算得出的FEV1预测百分比值低于PEF预测百分比值，平均差异为 -17.2%（95%可信区间 -16.3%，-18.1%）。在仅49.9%（598/1198）的测量值对中，哮喘严重程度的分类一致。不同的预测方程虽然不同程度地改变了错误分类的程度，但并未纠正依赖于使用FEV1或PEF评估哮喘严重程度的基本差异。
以预测值百分比表示的FEV1和PEF值并不等同。在进一步评估之前，作者建议已发布的哮喘指南应避免假定这两种测量结果相当。
