Normal spirometry with high and asthma-defining bronchodilator responsiveness: An appraisal from real-life data

Spirometric exercise in symptomatic patients (with/without suspicion of airflow obstruction) often ends with results showing normal pre-bronchodilator values.

We screened two different populations with prospectively archived spirometry, consisting of a) clinical suspicion of OAD (obstructive airway disease) and b) all other indications without any suspicion of OAD. Both populations underwent BDR (bronchodilator responsiveness) with salbutamol. We screened out the patients that displayed 'normal spirometry' [pre-bronchodilator (FEV1/FVC > 0.7 with FEV1 and FVC > 80%] and further looked for the presence of high (≥200 mL alone) or asthma-defining (>200 mL and 12%) BDR in them.

The two sets included 1019 and 3060 subjects in patients with or without suspected OAD. They showed the presence of 11.87% (121/1019) and 27.71% (848/3060) of normal spirometry. In the first set, 24.7% ( n = 30) and 17.35% ( n = 21), and in the second set, 12.26% ( n = 104) and 4.7% ( n = 40) patients had high (>200 mL) or asthma-defining (200 mL plus 12%) BDR. Thus, the asthma-defining BDR is present in 2.06% (21/1019) and 1.30% (40/3060) of patients with or without suspected OAD with normal pre-bronchodilator spirometry. The prevalence of isolated high BDR (200 mL) was present in 0.88% [9 (30-21) out of 1019] and 2.09% [ n = 64 (135-54)/3060] of them.

Some patients with respiratory symptoms with or without suspicion of airflow obstruction display pre-bronchodilator normal spirometry, and some of them demonstrate high or asthma-defining bronchodilator responsiveness. Performing BDR should be a routine in respiratory practice.