All issues > Volume 51(3); 2008

Original Article

Korean J Pediatr. 2008;51(3):323-328. Published online March 15, 2008.

Utility of a forced expiratory flow of 25 to 75 percent as a predictor in children with asthma

Jung Wan JW Kang¹, Kyung Won KW Kim¹, Eun Soo ES Kim¹, Jun Young JY Park¹, Myung Hyun MH Sohn¹, Kyu-Earn KE Kim¹

¹Department of Pediatrics and Institute of Allergy, Brain Korea 21 Project for Medical Sciences Biomolecule Secretion Research Center, Yonsei University College of Medicine, Seoul, Korea

Correspondence Myung Hyun MH Sohn ,Email: mhsohn@yumc.yonsei.ac.kr

Abstract

Purpose
: Asthma is defined as chronic inflammation of the lower small airways, and bronchial hyperreactivity (BHR) is a pathophysiologic feature of asthma. It has been proposed that although there is no direct variable capable of assessing the small airways, a forced expiratory flow of between 25 and 75 percent (FEF25-75) might be considered a more sensitive early marker of small airway obstruction than the forced expiratory volume in 1 second (FEV1). Thus, we proposed that the presence and degree of positive responses to bronchial methacholine testing were related to the difference (DFF) and ratio (RFF) between FEV1 and FEF25-75 in asthmatic children.
Methods
: The subjects were 583 symptomatic children, including 324 children with BHR and 259 controls. Pulmonary function tests, methacholine challenge tests, and skin prick tests were performed, and the total eosinophil count, total serum IgE, and serum eosinophil cationic protein level were measured in all subjects. From a concentration-response curve, the methacholine concentration required to produce a decrease of 20% from post-saline FEV1 was calculated (PC20).
Results
: The median DFF and RFF values decreased in controls compared to subjects with bronchial hyperresponsiveness, and this trend was found in groups ranked by its severity. PC20 had a negative correlation with DFF and RFF. Cutoff values of 0.5 for DFF and 1.042 for RFF were identified, and sensitivity and specificity were calculated.
Conclusion
: This study revealed that DFF and RFF might be predictive of bronchial hyperresponsiveness in the context of normal FEV1 in children.

Keywords :Asthma, Bronchial hyperresponsiveness, Forced expiratory flow between 25 and 75 percent, Forced expiratory volume in one second, Pulmonary function