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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.

Background: To avoid over-diagnosing of asthma-COPD overlap (ACO), a higher cut-off of 400mL for bronchodilator response (BDR) in FEV1 has been proposed for patients with asthma diagnosed at age ≥40 years. However, it is not known how many asthmatics fulfill this criterion and whether BDR is related to age at diagnosis of adult-onset asthma. Aim: To assess if BDR in FEV1 is related to age at diagnosis of adult-onset asthma and how many subjects fulfill the 400 mL criterion of BDR. Methods: 1030 patients with adult-onset asthma (age of onset ≥15 years) were included; 245 from SAAS (Seinajoki Adult Asthma Study) and 785 from COREA (Cohort for Reality and Evolution of Adult Asthma in Korea) cohorts, respectively. The BDR in FEV1 at the diagnosis of asthma was assessed. Patients were divided into groups based on age at asthma diagnosis: Results: BDR % in FEV1 did not differ between the groups with different age at asthma diagnosis. BDR % in FEV1 in age groups of Conclusion: BDR % in FEV1 at the diagnosis of adult-onset asthma does not vary according to age at diagnosis, and the limit of 400mL BDR in FEV1 is rarely reached. Our findings suggest that the cut-off for BDR of 400 mL has a low sensitivity to detect adult-onset asthma.