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Published on: April 14, 2010
Bronchodilator response in asthmatic children is significantly reduced when measured immediately after methacholine
Arvid W A Kamps1, Paul L P Brand, Karin Vermeer
1Department of Pediatrics, Division of Pulmonology, Isala Klinieken/Weezenlanden Hospital, PO Box 10500, Groot Wezenland 20, 8000 GM Zwolle, The Netherlands.
Insights
Performing a bronchodilator response (BDR) test immediately after a methacholine challenge in children with asthma is unreliable. The methacholine challenge significantly reduces the measured BDR, making it an unsuitable substitute for a separate test.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Clinical Asthma Research
Background:
- Bronchodilator response (BDR) and methacholine challenge tests are crucial for diagnosing and researching childhood asthma.
- Current clinical practice often requires separate testing sessions for BDR and methacholine challenges due to practical considerations.
Purpose of the Study:
- To investigate the feasibility and reliability of measuring BDR immediately following a methacholine challenge test in asthmatic children.
- To compare BDR measurements obtained with and without a preceding methacholine challenge.
Main Methods:
- Twenty-four children with asthma and hyperresponsiveness to methacholine underwent BDR testing on two separate days.
- BDR was assessed by measuring the change in forced expiratory volume in one second (FEV1) after salbutamol inhalation.
- On one day, BDR was measured immediately after a methacholine challenge; on the other, it was measured independently.
Main Results:
- A significant reduction in BDR was observed when measured after a methacholine challenge (5.2%) compared to when measured independently (10.8%).
- Post-bronchodilator FEV1%pred was also lower following the methacholine challenge.
- Baseline FEV1%pred did not differ significantly between the two testing conditions.
Conclusions:
- A methacholine challenge significantly attenuates the bronchodilator response in children with asthma.
- Measuring BDR immediately after a methacholine challenge is not a reliable substitute for a standalone bronchodilator test.
- Separate testing sessions are necessary for accurate BDR assessment in pediatric asthma evaluations.
Aim:
Airway responses to a bronchodilator (BDR) and to methacholine are frequently measured in the assessment of childhood asthma and in pulmonary research. For practical reasons, we wondered whether it would be possible to obtain a reliable BDR immediately after completion of a methacholine challenge test. To this end, we compared BDR with and without a preceding methacholine challenge.
Methods:
The BDR was measured twice in random order on consecutive days in 24 asthmatic children with methacholine hyperresponsiveness. It was calculated as the change in forced expiratory volume in one second (FEV1) before and 20 min after inhaling 800 microg of salbutamol (metered dose inhaler with a spacer), expressed as a percentage of the predicted value (deltaFEV1%pred). On one day BDR was measured immediately after completing a methacholine challenge, on the other day without any preceding challenge.
Results:
Mean(SD) baseline FEV1%pred was not significantly different between test days [98.6(14.2)% and 98.1(13.8)%, respectively, p=0.53]. The geometric mean provocative dose of methacholine producing a 20% fall in FEV1 (PD20) was 56.2 microg (range 10.3-306.2 microg). The mean (SEM) BDR without preceding methacholine challenge was 10.8(1.4)%, while after preceding methacholine challenge it was 5.2(1.5)% (mean difference 5.6%, 95% CI 3.0%-8.1%, p<0.001). Mean(SEM) postbronchodilator FEV1%pred was 109.4(3.0)% without and 103.4(2.7)% with preceding methacholine challenge (mean difference 6.0%, 95% CI 3.5%-8.6%, p<0.001).
Conclusion:
A preceding methacholine challenge significantly reduces BDR in asthmatic children. Therefore, a BDR, measured immediately after completing a methacholine challenge, cannot be used as a substitute for a separate bronchodilator test.
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