The Response to Bronchodilators in Adults is not Predictive of Bronchial-hyperreactivity

Abstract

Background. In some subjects with suspected asthma who have normal spirometry, administration of bronchodilators (BD) improves expiratory flow rates. The predictive value of this phenomenon in adults is not known. Objectives. To evaluate the predictive value of the response to BD for bronchial hyper-responsiveness (BHR) using the metacholine challenge test (MCT). Patients and methods. The study population included 62 non-smoking adult patients (41.9% women) 29.5 ± 15.5 years of age (range 18–64 years) with suspected asthma with normal spirometry that underwent MCT within 1 week. The response to BD (200 μ g inhaled salbutamol) was compared between subjects with positive and negative MCT using cutoff levels of provocative concentrations of metacholine causing a 20% decrease in forced expiratory volume in 1 second (FEV₁) (PC₂₀) of 4 and 8 mg/mL. Results. Mean (± SD) baseline FEV₁ was 87.8 ± 12% of predicted. After BD administration the mean FEV₁ increased by 4.3 ± 3.9%. The prevalence of BHR was 17.7% and 25.8% for PC₂₀ for PC₂₀ of 4 mg/mL and 8 mg/mL, respectively. The post-BD FEV₁ increment for subjects with positive and negative MCT tests was 3.9% ± 3.3% versus 4.4% ± 4.1%, respectively; p = 0.89, using cutoff of 4 mg/mL. The corresponding figures for cutoff of 8 mg/ml were 4.3% ± 3.1% vs. 4.3% ± 4.2%, respectively; p = 0.8465. There was no correlation between post-BD FEV₁ increment and PC₂₀ values in patients with positive MCT test for the above-mentioned cutoff levels (correlation coefficient r = 0.1645, p = 0.6289; and r = 0.2417, p = 0.4051, respectively). Conclusions. In adults with suspected asthma who have normal spirometry, the response to BD cannot be used to predict BHR.

Keywords:

• bronchial asthma
• bronchial hyper-responsiveness