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Airway hyperresponsiveness in patients with normal spirometry results and symptoms compatible with asthma: Primary
Amy Chen1, Katrina A D'Urzo2, Anthony D D'Urzo3
1Family medicine resident in the Department of Family and Community Medicine at the University of Toronto in Ontario.
Objective:
To evaluate the proportion of patients with symptoms suggestive of asthma and normal lung function who exhibit airway hyperreactivity with methacholine challenge testing (MCT) in primary care.
Design:
Retrospective chart review.
Setting:
Primary care lung clinic in Toronto, Ont.
Participants:
A total of 69 patients presenting to the lung clinic who had symptoms compatible with asthma, normal spirometry test results, and were referred for MCT.
Main Outcome Measures:
Descriptive statistics, frequency counts, independent t tests, and 2 tests were used to examine differences in the proportion of clinical and demographic variables identified in patients with or without a positive MCT result. Effect size was determined between MCT-positive and MCT-negative patients for both categorical ( coefficient) and continuous (Hedges g) data.
Results:
Twenty-one patients (30.4%) had positive MCT results, and 48 patients (69.6%) had negative MCT results. Family history of asthma and reduced baseline and postbronchodilator forced expiratory volume in 1 second were associated with a positive MCT result.
Conclusion:
The findings of this study provide insight into the utility of simple spirometry for asthma diagnosis and the need to further clarify the role of MCT in the primary care setting.
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