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Discriminative capacity of bronchodilator response measured with three different lung function techniques in
1Department of Pediatrics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
Insights
Specific airway resistance (sRaw) effectively distinguishes asthma in young children. This lung function test shows significant bronchodilator response, aiding asthma diagnosis in this age group.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Diagnostic Accuracy
Background:
- Diagnosing asthma in children aged 2-5 years presents clinical challenges.
- Objective measures of bronchodilator responsiveness are needed for accurate asthma diagnosis in young children.
Purpose of the Study:
- To quantify and compare bronchodilator responsiveness in healthy and asthmatic children aged 2-5 years.
- To evaluate the diagnostic capacity (sensitivity, specificity) of different lung function tests for asthma in this age group.
Main Methods:
- Ninety-two children (37 healthy, 55 asthmatic) underwent lung function tests: specific airway resistance (sRaw), interrupter technique resistance (Rint), and impulse oscillation (Rrs5, Xrs5).
- Measurements were taken before and after terbutaline inhalation.
- Healthy children had a randomized, double-blind, crossover design; asthmatic children had an open study.
Main Results:
- Asthmatic children exhibited significantly poorer baseline lung function compared to healthy controls across all tested methods.
- All tested lung function parameters (sRaw, Rint, Rrs5) improved significantly in healthy children post-terbutaline, unlike Xrs5.
- Bronchodilator response was significantly greater in asthmatic children than in controls for all methods.
- Specific airway resistance (sRaw) demonstrated the highest discriminative power, with 66% sensitivity and 81% specificity for asthma diagnosis at a 25% decrease threshold.
Conclusions:
- Bronchodilator response measured by sRaw effectively differentiates asthmatic from healthy young children.
- sRaw measurement offers a valuable tool to aid in defining asthma in young children, a population that is clinically difficult to manage.
- The diagnostic accuracy of sRaw for asthma in this age group surpasses that of Rint, Rrs5, and Xrs5.
Abstract:
The primary aim of this study was to quantify and compare bronchodilator responsiveness in healthy and asthmatic children aged 2 to 5 yr. The secondary aim of the study was to compare discriminative capacity (i.e., sensitivity, specificity, and predictive values of the reversibility test for the diagnosis of asthma) for each of the lung function tests applied in the study. Specific airway resistance (sRaw) as measured by whole-body plethysmography, respiratory resistance as measured with the interrupter technique (Rint), and respiratory resistance and reactance at 5 Hz (Rrs5, Xrs5, respectively) as measured with the impulse oscillation technique were assessed before and 20 min after inhalation of terbutaline from a pressurized metered-dose inhaler via a metal spacer by 92 children (37 healthy controls and 55 asthmatic subjects). The study of healthy children followed a randomized, double-blind, crossover design, whereas the study of asthmatic children was open. Baseline lung function was significantly decreased in asthmatic children as compared with healthy control subjects as reflected by all techniques used in the study. sRaw, Rint, and Rrs5, but not Xrs5, improved significantly with terbutaline as compared with placebo in healthy control subjects. Lung function improved to a significantly greater extent in asthmatic children than in control subjects as reflected by all methods. sRaw provided the best discriminative power of such a bronchodilator response, with a sensitivity of 66% and specificity of 81% at the cutoff level of a 25% decrease in sRaw after bronchodilator administration. In conclusion, bronchodilator response measured by sRaw allows a separation of asthmatic from healthy young children. This may help define asthma in this clinically difficult-to-manage group of young wheezy children. The sensitivity and specificity of the other methods used in the study were less than those of sRaw.