Methacholine-induced fall in forced vital capacity as a marker of asthma severity.

Content Provider	Semantic Scholar
Author	Abisheganaden, John Arputhan Chan, Chung Chow Chee, Cynthia Bin-Eng Wang, Yee Tang Sonny
Copyright Year	1999
Abstract	The dose of methacholine causing a 20% fall in forced expiratory volume in 1 sec (FEV1) from baseline (PD20) has been used as an index of asthma severity. The aim of this study was to determine if the percentage fall in forced vital capacity (FVC) from baseline at the PD20 (dFVC%) is an independent marker of asthma severity. We first retrospectively studied the dFVC% and PD20 obtained from 149 consecutive newly diagnosed asthmatics with a positive methacholine-challenge test (MCT). We then performed MCT on 20 normal subjects and 35 stable asthmatics. The 'milder' asthmatics (n = 20) and 'more severe' asthmatics (n = 15) were on regular inhaled corticosteroids: 200 micrograms or less and 800 micrograms or more daily, respectively. A dosimeter technique was used, and normal subjects were given a cumulative dose of 2400 micrograms. The PD20 and dFVC% were calculated using log-linear interpolation of the last two points. Student's unpaired t-tests and linear regression analyses were used for comparison and correlation of results. There was no significant correlation between dFVC% and PD20 among the 149 newly diagnosed asthmatics (r = 0.1), or among the 35 known stable asthmatics (r = 0.008). The more severe asthmatics had a larger dFVC% compared with the milder asthmatics (15.8% vs. 9.6%; P = 0.0005). In addition, inhaled corticosteroid usage correlated better with dFVC% (r = 0.56) than with PD20 (r = 0.36). The normal subjects had a mean fall in FVC of only 4.8%. The percentage fall in FVC at PD20 (dFVC%) may be a useful index of asthma severity which is independent of PD20. This index is potentially complementary to the PD20 in the assessment of asthma severity.
File Format	PDF HTM / HTML
Alternate Webpage(s)	https://core.ac.uk/download/pdf/82573776.pdf
PubMed reference number	10464893v1
Volume Number	93
Issue Number	4
Journal	Respiratory medicine
Language	English
Access Restriction	Open
Subject Keyword	Adrenal Cortex Hormones Asthma Dosimeter, device Expiration, function Forced expiratory volume function Inspiration function Large Linear IgA Bullous Dermatosis Methacholine Pulmonary Function Test/Forced Expiratory Volume 1 Regression Analysis
Content Type	Text
Resource Type	Article