Canadian Thoracic Society 2021 Guideline update: Diagnosis and management of asthma in preschoolers, children and adults

Diagnosing asthma and chronic obstructive pulmonary disease

“…However, given that methacholine challenge testing is often even more difficult to access than spirometry, this strategy might be difficult to implement efficiently in some settings. Another diagnostic approach suggested in guidelines 4 -a substantial (≥12%) improvement in FEV 1 with therapeutic trial-may be more realistic in such settings. Another option may be to have patients gradually decrease therapies as long as they remain asymptomatic; methacholine challenge testing would then be requested only once they have stopped taking all therapies.…”

“…1 These complaints often lead to diagnoses of asthma or COPD, which are among the most commonly diagnosed chronic diseases, with approximately 11% of the Canadian population carrying a diagnostic label of asthma and 6% a label of COPD. 2 Although guidelines clearly recommend that a diagnosis of asthma or COPD requires pulmonary function testing 3,4 (starting with spirometry and a bronchodilator response test), studies show that only 43% of Canadian patients who received a diagnostic label of asthma 5 and 36% of those with a label of COPD 6 had a pulmonary function test (PFT) within 1 year before or after their diagnoses.…”

“…Accordingly, for both conditions, guidelines recommend objective testing, starting with spirometry with bronchodilator response testing in anyone 6 years of age or older. 3,4,14,21 In asthma, diagnosis requires the presence of obstruction (ie, a reduced forced expiratory volume in the first second [FEV 1 ] to forced vital capacity ratio) and an improvement in the FEV 1 of at least 12% and 200 mL from the baseline value after administration of the bronchodilator. 4 Although this finding is sufficient to make the diagnosis, if a bronchodilator response is absent, it does not rule out asthma.…”

“…3,4,14,21 In asthma, diagnosis requires the presence of obstruction (ie, a reduced forced expiratory volume in the first second [FEV 1 ] to forced vital capacity ratio) and an improvement in the FEV 1 of at least 12% and 200 mL from the baseline value after administration of the bronchodilator. 4 Although this finding is sufficient to make the diagnosis, if a bronchodilator response is absent, it does not rule out asthma. Among patients suspected of having asthma, about 40% will have a falsely negative bronchodilator response test result 27 and require a methacholine challenge test for diagnosis.…”

Diagnosis and management of asthma in children

“…Additionally, the symptom onset for most cases of paediatric asthma occurs before the age of 3 years29 when lung function testing cannot be used to aid diagnosis. In this age group, response to an asthma treatment trial is useful to aid diagnostic decision making and is recommended in a number of national guidelines 27 30–32…”