Allergy Asthma Respir Dis.  2021 Jul;9(3):141-147. 10.4168/aard.2021.9.3.141.

Analysis of PC₂₀-FEF_25%-75% and △FVC in the methacholine bronchial provocation test

• Kim HA
• Kwon JE
• Ahn JY
• Choe JY
• Kim DS
• Park SH
• Hyun MC
• Choi BS

• KMID: 2519024
• DOI: http://doi.org/10.4168/aard.2021.9.3.141

Abstract

Purpose
Forced expiratory flow between 25% and 75% (FEF _25%-75%) is known to sensitively reflect bronchial obstruction. Methacholine challenge test (MCT) has shown varying reduction levels of forced vital capacity (FVC) with the reduction in forced expiratory volume in 1 second (FEV₁) in asthma. The aim of this study was to evaluate the clinical implication of provocative concentration causing a 20% fall in FEF _25%-75%(PC ₂₀-FEF _25%-75%) and the percentage fall in FVC at the PC ₂₀ dose of methacholine (△FVC).
Methods
A total of 194 children who visited the hospital due to respiratory symptoms and underwent MCT were analyzed retrospectively. The patients were divided into 3 groups. Group I had both PC ₂₀-FEV₁ and PC ₂₀-FEF _25%-75% above 16 mg/mL; group II had a PC ₂₀-FEF _25%-75% that fell below 16 mg/mL but PC ₂₀-FEV₁ was 16 mg/mL or above; group III had a PC ₂₀-FEV₁and a PC ₂₀-FEF _25%-75% that both fell below 16 mg/mL.
Results
In group II, PC ₂₀-FEV₁ was lower (P = 0.026) and the rate of change in FEV₁ and FEF _25%-75% from baseline to 16 mg/mL of methacholine concentration was greater than in group I (both P< 0.001). Levels of PC ₂₀-FEF _25%-75% were higher in group II compared to group III (P < 0.001). △FVC showed a correlation with PC ₂₀-FEV₁ (P < 0.001) only in the whole group.
Conclusion
In asthmatic children, PC ₂₀-FEF _25%-75% may be associated with bronchial hyperresponsiveness. △FVC was not associated with other parameters in either group. For subjects with a positive finding of PC ₂₀-FEF _25%-75% and a negative finding of MCT, the progression to asthma can be suspected.

Keyword

Methacholine challenge test; Asthma; Child; Vital capacity; Forced expiratory flow