A comparison in a Saskatchewan population between clinical diagnosis of asthma and American Thoracic Society Forced Expiratory Volume at one second (FEV1) post-bronchodilator improvement criteria

Background: The diagnosis of asthma can be challenging and is based on clinical symptoms, physical examination, and pulmonary function tests. Most patients with asthma will have a significant post-bronchodilator response on spirometry indicating airway hyper-responsiveness. However, having a significant bronchodilator response by itself is not diagnostic of asthma. Also, the definition of a "significant" response is controversial. Many respirologists use the American Thoracic Society (ATS) post-bronchodilator response criteria of 12% (provided it is ≥ 200 ml) improvement in FEV1 (or FCV) from the baseline spirometry. -- Methods: This study retrospectively reviewed 644 patients who met the ATS criteria for a significant post-bronchodilator spirometric response. The staff respirologist's diagnosis of asthma, based on all clinical and pulmonary function data, was used as the standard for the diagnosis of asthma. -- Results: It was found that relying on spirometric criteria alone was inadequate in asthma diagnosis as only 54.7% of 310 patients meeting ATS bronchodilator response criteria were felt to have asthma clinically. Increasing the post-bronchodilator percent improvement from the ATS criteria only marginally improved diagnostic specificity and resulted in a decline in sensitivity. -- Conclusions: This further emphasizes the need to use spirometric criteria as a guide but not as an unimpeachable gold standard by which to make a diagnosis of asthma. The diagnosis of asthma depends on a combination of expert physician correlation of history, physical examination, and pulmonary function test results