This study is a cross-sectional study. Thai patients aged 18 years or older with severe asthma are included in the study. Participants will complete two questionnaires about asthma control: the Global Initiative for Asthma (GINA) and the Asthma Control Test (ACT), and will perform spirometry, a fractional exhaled nitric oxide (FeNO) test, and blood eosinophil counts (BEC).
