What is the minimum percentage change in FEV1 after bronchodilator administration that is diagnostic for asthma?

In diagnosing asthma, a recognized and clinically significant response to bronchodilator administration is reflected by a change in Forced Expiratory Volume in one second (FEV1). The minimum percentage change in FEV1 that indicates a positive bronchodilator response, specifically for asthma, is 12% or more from the baseline measurement. This threshold stems from research indicating that this level of improvement is both clinically relevant and supports the diagnosis of asthma due to its typical pathophysiology involving variable airway obstruction.

A change of 12% also accounts for variances in normal physiological measurements, providing a clearer indication that the airflow limitation can be reversed with bronchodilators, a hallmark of asthma. When evaluating an individual suspected of having asthma, this percentage serves as a critical diagnostic criterion for confirming the condition.

In contrast, lower percentages would not adequately establish a diagnosis of asthma, as they may result from normal variability in waveform fluctuation or other non-asthmatic conditions, thus underscoring the importance of the 12% threshold in clinical practice.