BACKGROUND: Asthma is a disease characterized by variable airflow obstruction, but the measurement of airflow is often omitted in the process of diagnosis and management of the disease.OBJECTIVES: Features of asthma severity and control were examined to determine the extent to which objective measurements, including forced expiratory volume in 1 s and forced expiratory volume in 1 s/forced vital capacity, correlated with other manifestations of the disease.METHODS: Subjects were a consecutive sample of patients with asthma attending a university-based asthma clinic. All subjects underwent routine assessment using a standard questionnaire and spirometry.RESULTS: A total of 500 subjects were included in the present study, and their assessment showed that neither symptoms nor history could predict or be predicted by their measurements of lung function.CONCLUSION: Routine measurement of lung function should be performed on subjects with asthma if normal or near-normal lung function is a desired component of asthma control.