Appropriate diagnosis of respiratory illness can be challenging in clinical settings. A prospective, multicenter cohort study found that as many as 1 in 3 adults who had been diagnosed with asthma were found to have no current evidence of the condition,1 underscoring the importance of identifying accurate diagnostic tests.
Study Compares Asthma Tests
Researchers at the University of Liège in Belgium compared methacholine bronchial challenge with bronchodilation to salbutamol in the same patient population. Their findings were published in the Journal of Allergy and Clinical Immunology.2
Drawing from the University of Liège Hospital Center asthma clinic database, the investigators identified 194 untreated patients with intermittent or chronic respiratory symptoms who had been referred by clinicians for a potential asthma diagnosis. All patients had baseline FEV1 >70% predicted and underwent each test 7 to 14 days apart. A positive bronchial challenge test was a ≥20% decrease in FEV1 with a provocative concentration of methacholine of ≤16 mg/mL. A positive bronchodilation test was reversibility ≥12% from baseline and 200 mL with 400 μg inhaled salbutamol.
Agreement Found to Be Rare
The researchers found that 91% of patients had either positive methacholine challenge or positive bronchodilation to inhaled salbutamol. Less than 10% of patients tested negative to both tests. Isolated positive methacholine challenge was found in 71% of patients, and isolated positive bronchodilation was found in 3%. Double-positive tests were identified in 17% of patients.
In all, methacholine challenge identified 96% of patients with asthma, while significant reversibility to inhaled salbutamol was seen in 22%. Among patients receiving a diagnosis of asthma, the agreement between the tests was 19%.
Methacholine Challenge Outperforms Bronchodilation to Salbutamol
The authors concluded that “methacholine challenge outperforms reversibility to salbutamol to diagnose asthma without selecting patients with distinct inflammatory profile.” The study “re-emphasizes that a lack of significant reversibility to salbutamol is common in patients with symptoms suspected to be due to asthma and should prompt the performance of a methacholine challenge to confirm the diagnosis.”
- Aaron SD, Vandemheen KL, FitzGerald JM, et al; for the Canadian Respiratory Research Network. Reevaluation of diagnosis in adults with physician-diagnosed asthma. JAMA. 2017;317(3):269-279.
- Louis R, Bougard N, Guissard F, Paulus V, Henket M, Schleich F. Bronchodilation test with inhaled salbutamol versus bronchial methacholine challenge to make an asthma diagnosis: do they provide the same information? [published online September 18, 2019] J Allergy Clin Immunol Pract. doi: 10.1016/j.jaip.2019.09.007