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(Chest. 2006;130:1454-1461.)
© 2006 American College of Chest Physicians

The Relationship Between FEV1 and Peak Expiratory Flow in Patients With Airways Obstruction Is Poor*

Ashutosh N. Aggarwal, MD, FCCP; Dheeraj Gupta, MD, FCCP and Surinder K. Jindal, MD, FCCP

* From the Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India.

Correspondence to: Surinder K. Jindal, MD, FCCP, Professor and Head, Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh 160012, India; e-mail: skjindal{at}indiachest.org

Abstract

Study objectives: To evaluate the correlation between FEV1 and peak expiratory flow (PEF) values expressed as a percentage of their predicted value, and to assess factors influencing differences between the two measurements.

Design: Cross-sectional.

Setting: Pulmonary function laboratory at a tertiary-level teaching hospital in northern India.

Participants: A total of 6,167 adult patients showing obstructive pattern on spirometry over a 6-year period.

Interventions: None.

Measurements and results: There was considerable variability between percentage of predicted FEV1 (FEV1%) and percentage of predicted PEF (PEF%). Locally weighted least-square modeling revealed that PEF% overestimated FEV1% in patients with less severe obstruction and underestimated it in those with more severe obstruction. Using Bland-Altman analysis, PEF% underestimated FEV1% by a mean of only 0.7%; however, limits of agreement were wide (– 27.4 to + 28.8%), indicating that these two measurements cannot be used interchangeably. PEF% and FEV1% were > 5% apart in approximately three fourths and differed by > 10% in approximately one half of the patients. On multivariate analysis, discordance > 5% was significantly influenced by female gender (odds ratio, 1.26; 95% confidence interval [CI], 1.01 to 1.58) and increasing FEV1% (odds ratio, 1.09 for every 10% increase; 95% CI, 1.04 to 1.14) but not by height or age.

Conclusions: FEV1% and PEF% are not equivalent in many patients, especially women and those with less severe airflow limitation. Assumptions of parity between PEF% and FEV1% must be avoided.

Key Words: agreement • airflow limitation • respiratory function tests






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