Several studies have shown considerable disagreement when using the FEV₁ and PEFR to assess the severity of an airflow obstruction. A differential classification of the severity of asthma would lead to serious differences in the evaluation and management of asthma. The aim of this study was to examine the relationship between the FEV₁ and PEFR in asthma patients with mild symptoms.

In this study, the PEFR and FEV₁ were obtained from 92 adult asthma patients with mild symptoms attending an outpatient pulmonary clinic. The mean differences and the limits of agreement in the paired measurements of the FEV₁ and PEFR were calculated.

There was a considerable correlation between the FEV₁ and PEFR measurements when expressed as a % of the predicted values (r=0.686, p<0.01). The 95% limit of agreement (mean difference ±1.96SD) between the FEV₁ % and PEFR % were acceptable(-27.4%^~33.8%). In addition, the weighted κ(kappa) coefficient for the agreement between the FEV₁ % and PEFR % was 0.74 (95% CI, 0.63-0.81), indicating excellent agreement between the two measurements.

The spirometer (FEV₁) and the Mini-Wright peak flow meter (PEFR) can be used interchangeably in adult asthma patients with mild symptom.