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Methacholine inhalational challenge in the evaluation of chronic cough in children
Insights
Methacholine (MCH) bronchial challenge helps diagnose cough variant asthma in children with chronic cough. Positive MCH responses indicate likely benefit from bronchodilator therapy, even with normal initial lung function tests.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Clinical Diagnostics
Background:
- Chronic cough is a common pediatric complaint.
- Diagnosing cough variant asthma can be challenging, often presenting with normal baseline lung function.
- Identifying children who will benefit from asthma treatment is crucial.
Purpose of the Study:
- To evaluate the diagnostic utility of methacholine (MCH) bronchial challenge in children with chronic cough.
- To determine if MCH challenge can identify patients with cough variant asthma.
- To assess the correlation between MCH response and clinical/spirometric parameters.
Main Methods:
- Retrospective analysis of 58 children (7-16 years) with chronic cough.
- Performed methacholine (MCH) bronchial challenge tests.
- Assessed baseline lung function, including residual volume/total lung capacity (RV/TLC) and midexpiratory flow rate (FEF25-75).
- Evaluated response to bronchodilator therapy (albuterol/theophylline).
Main Results:
- 31 of 58 children had a positive MCH response, not predictable by clinical criteria or spirometry.
- MCH-positive patients showed a significantly higher RV/TLC ratio.
- 27/31 MCH-positive patients responded to bronchodilator therapy, confirming cough variant asthma.
Conclusions:
- Methacholine (MCH) bronchial challenge is valuable for diagnosing cough variant asthma in children with chronic cough.
- The test identifies patients likely to respond to bronchodilator therapy, irrespective of initial lung function.
- Consider MCH challenge for children with unexplained chronic cough to guide asthma treatment.
Abstract:
The medical records of 58 children (age range, 7 to 16 years) who presented with chronic cough were retrospectively analyzed to determine the value of methacholine (MCH) bronchial challenge in reaching a specific diagnosis. Baseline lung function tests were normal in all subjects, apart from an elevated residual volume/total lung capacity ratio (RV/TLC) in 11 patients, and a reduced midexpiratory flow rate (FEF25-75) in five of these patients. Thirty-one patients had a positive response to MCH, but these patients could not be identified on the basis of clinical criteria or spirometric parameters. MCH-positive patients did have a significantly higher RV/TLC than did MCH-negative patients. Twenty-seven of the 31 MCH-positive patients responded to a trial of bronchodilator therapy (albuterol/theophylline), confirming the diagnosis of cough variant asthma in these patients. We conclude that children with chronic cough should be considered for methacholine challenge in order to identify patients who are likely to benefit from specific bronchodilator therapy.