What is the hallmark parameter for diagnosing asthma?

The hallmark parameter for diagnosing asthma is FEV1, which stands for Forced Expiratory Volume in one second. This measure assesses how much air a person can forcibly exhale in the first second of a breath and is crucial for understanding lung function.

In asthma, the airways become inflamed and narrowed, making it difficult to breathe. A significant finding in asthma is a reduction in FEV1 due to this obstruction. Furthermore, when patients with asthma are given bronchodilators, a significant improvement in FEV1 typically occurs, demonstrating the reversible nature of the airflow obstruction associated with asthma.

While the FEV1/FVC ratio is also important in the diagnosis of asthma, especially to determine whether there is obstruction or restriction, it is the FEV1 measurement that is most directly reflective of the airway obstruction that characterizes asthma. Pulse oximetry is useful for assessing oxygen saturation but does not provide information about airway function, and peak flow measurement can be helpful for monitoring asthma control but is less definitive for diagnosis. Thus, FEV1 remains the primary focus in the diagnostic process for asthma.