Extensively used current guidelines of the American Thoracic Society/European Respiratory Society (ATS/ERS) define a positive aerosolized bronchodilator (BD) response as: “…an increase in FEV₁ and/or FVC≥12% of control and ≥200mL.” We hypothesized that BD responsiveness was better assessed using a statistical approach, linked to each individual's spirometric measurements, rather than the variability of others.

We retrospectively analyzed 1-year's pre- and post-BD spirometric tests from our hospital's clinical laboratory. Using measurements of forced expiratory volume in 1-s (FEV₁), forced expiratory volume in 3-s (FEV₃), and forced vital capacity (FVC) from each of three satisfactory forced pre-BD and three satisfactory forced post-BD spirometric maneuvers, we classified each of 313 consecutive patient studies as responders or non-responders in two ways. First, we used ATS/ERS guideline criteria based on population variability. Second, we used unpaired, single-tailed t-tests at P<0.05 for FEV_1, FEV_3, and FVC, considering the variability of and difference between each individual's pre- and post-BD maneuvers.

135 studies were both ATS/ERS and t-test non-responders, three were ATS/ERS responders and t-test non-responders, 86 were ATS/ERS and t-test responders, and 89 were ATS/ERS non-responders and t-test responders. The latter 89 included many patients with either low baseline FEV₁ (<1.50L) who could not reach the 200mL increase criterion or high baseline FEV₁ (>3.00L) who could not reach the 12% increase criterion.

We believe individual t-tests may categorize patient's BD responsiveness better than ATS/ERS guideline criteria which are based on population responses and require both fixed volume and percentage changes. Its usefulness by others remains to be shown.