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Methacholine inhalation challenge in young children: results of testing and follow-up
A D Adinoff1, R T Schlosberg, R C Strunk
1National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado.
Insights
Methacholine inhalation challenges (MIC) are safe and effective for diagnosing asthma in young children with uncertain diagnoses. A positive MIC indicates increased bronchial reactivity, supporting an asthma diagnosis.
Area of Science:
- Pediatric Pulmonology
- Allergy and Immunology
- Diagnostic Medicine
Background:
- Diagnosing asthma in young children is challenging due to atypical symptoms and inability to perform standard pulmonary function tests.
- Recurrent respiratory symptoms in children aged 1-5.8 years often raise diagnostic uncertainty for asthma.
Purpose of the Study:
- To evaluate the safety and efficacy of methacholine inhalation challenges (MIC) for diagnosing asthma in young children.
- To assess the correlation between positive MIC results and the long-term clinical course of respiratory symptoms.
Main Methods:
- Methacholine inhalation challenges (MIC) were performed on 24 children (1-5.8 years) with uncertain asthma diagnoses.
- Testing involved either a 5-breath or 1-minute inhalation technique until symptoms or a maximum concentration (5-25 mg/mL) was reached.
- Patients were followed for 0.5-3.8 years post-challenge.
Main Results:
- Eighteen out of 24 patients had positive MIC results, with a mean provocative dose of 3.0 mg/mL.
- No serious or delayed adverse reactions were observed; symptoms resolved with bronchodilators.
- All patients with positive MICs experienced persistent respiratory symptoms and required bronchodilator treatment, unlike most with negative MICs.
Conclusions:
- Methacholine inhalation challenges (MIC) are a safe diagnostic tool for uncertain asthma cases in young children.
- A positive MIC result in this population signifies increased bronchial reactivity and supports a clinical asthma diagnosis.
- MIC findings correlate with the long-term need for asthma management and medication.
Abstract:
The diagnosis of asthma is often difficult in young children because their symptoms may not be typical and pulmonary function testing cannot be performed by the patient. We therefore performed methacholine inhalation challenges (MIC) in 24 patients 1 to 5.8 years of age in whom the diagnosis of asthma was uncertain. These patients had histories of recurrent respiratory symptoms for a mean duration of 2.4 years (range = 0.5 to 5.1) in the absence of other systemic diseases. Testing was done by either the 5-breath technique or 1-min inhalation via face mask until wheezing or coughing and retractions developed or a maximum methacholine concentration of 5 to 25 mg/mL was reached. Eighteen MIC were positive and six negative. The mean provocative dose was 3.0 mg/mL (range = 0.6 to 10). No patients suffered serious or delayed reactions and all symptoms reversed with inhaled bronchodilators (BD). During the MIC, the progression of symptoms often mimicked progression of those observed in the past and was useful in teaching the parents. Patients were followed for 0.5 to 3.8 years (mean = 2.3). All patients with a positive MIC have continued to have recurrent respiratory symptoms and require regular or intermittent BD. Only one patient with a negative MIC at 5 mg/mL has recurrent respiratory symptoms and requires daily BD 3 years after the initial evaluation. We conclude that MIC can safely be performed in young children in whom the diagnosis of asthma is uncertain. A positive MIC in this context demonstrates increased bronchial reactivity and is supportive of a clinical diagnosis of asthma.(ABSTRACT TRUNCATED AT 250 WORDS)