Immediate bronchodilator response in FEV as a diagnostic criterion for adult asthma.

Asthma is characterised by variable and reversible expiratory airflow limitations. Thus, it is logical to use the change in forced expiratory volume in 1 s (FEV) in response to a bronchodilator (ΔFEVBDR) as a diagnostic tool; increases of ≥12% and ≥200 mL from the baseline FEV are commonly used values. We aimed to evaluate the historical development of diagnostic cut-off levels for the ΔFEVBDR for adults and the evidence behind these recommendations.We searched for studies from the reference lists of all the main statements, reports and guidelines concerning the interpretation of spirometry and diagnostics for asthma and conducted a literature search.A limited amount of evidence regarding the ΔFEVBDR in healthy populations was found, and even fewer patient studies were found. In healthy persons, the upper 95th percentile for the absolute ΔFEVBDR ranges between 240 mL and 320 mL, the relative ΔFEVBDR calculated from the initial FEV ranges from 5.9% to 13.3% and the ΔFEVBDR calculated from the predicted FEV ranges from 8.7% to 11.6%. However, the absolute and percentage ΔFEVBDR values calculated from the initial FEV are dependent on age, sex, height and the degree of airway obstruction. Thus, the use of the ΔFEVBDR calculated from the predicted FEV might be more appropriate.Not enough data exist to assess the sensitivity of any of the cut-off levels for the ΔFEVBDR to differentiate asthma patients from healthy subjects. Further studies in newly diagnosed asthma patients are needed.