Clinical value of the immediate bronchodilator response to diagnose asthma in steroid-naïve adults

Background: Measurement of spirometry with bronchodilator response has been recommended to detect asthma. However, the diagnostic value of bronchodilator response in newly diagnosed steroid-naive adult patients with asthma remains unknown. Aims and Objectives: To evaluate the sensitivity of bronchodilator response in FEV1 as a diagnostic test for asthma in a real-life cohort of Seinajoki Adult Asthma Study (SAAS). Methods: In the diagnostic phase 369 spirometries with bronchodilation test were made for 219 steroid-naive patients. Fulfilments of three different thresholds of bronchodilator tests; ∆FEV1 ≥12% and ≥200mL, or ≥15% and ≥400mL of initial FEV1 and ∆FEV1 ≥9% of predicted FEV1 were measured. According to the NICE algorithm study patients were also separated to obstructive and non-obstructive groups according to the spirometry with the highest ∆FEV1%. Results: Of the total cohort, 35.6% fulfilled ∆FEV1 ≥12% and ≥200mL of initial FEV1, 18.3% fulfilled ∆FEV1 ≥15% and ≥400mL of initial FEV1 and 36.1% fulfilled ∆FEV1 ≥9% of predicted FEV1 at least on one occasion. One third (31%) of these steroid-naive patients were obstructive (pre FEV1/FVC Conclusions: In steroid-naive patients, the currently used thresholds of bronchodilator response have low sensitivity (18-36%) to diagnose asthma in adults. In obstructive patients, sensitivity is somewhat higher (27-56%) but far from optimal. If asthma suspicion exists after spirometry, further lung function tests need to be considered.