Diagnostic Approach to Wheezing

Initial Assessment and Spirometry

The American College of Physicians recommends performing spirometry to confirm airflow obstruction and guide treatment decisions when wheezing is detected on auscultation, especially in patients with a significant smoking history (>55 pack-years) and patient-reported wheezing, as this combination strongly predicts airflow obstruction 1
Assess for accompanying symptoms such as dyspnea, chronic cough, chest tightness, or exercise limitation, as these indicate symptomatic respiratory disease requiring intervention 1
Calculate pack-years, as >40 pack-years has a positive likelihood ratio of 12 for airflow obstruction, and >55 pack-years combined with wheezing essentially confirms obstruction 1
The combination of >55 pack-year smoking history, wheezing on auscultation, and patient self-reported wheezing has a likelihood ratio of 156 for airflow obstruction 1
Confirm airflow obstruction using spirometry with bronchodilator testing, looking for a post-bronchodilator FEV1/FVC ratio <0.70, and determine severity based on FEV1 percent predicted 1
Assess reversibility by looking for ≥15% and ≥200 mL increase in FEV1 or ≥20% and ≥60 L/min increase in PEF after bronchodilator 2

Guide treatment decisions based on spirometry results, as symptomatic patients with FEV1 <60% predicted benefit from inhaled treatments (anticholinergics, long-acting β-agonists, or corticosteroids) 3
Do not use spirometry to screen asymptomatic patients, even with risk factors, as this leads to unnecessary testing, costs, disease labeling, and potential harm from treatment without proven benefit 1, 3
Initiate short-acting β-agonist therapy while awaiting formal evaluation, and objectively assess response by documenting improvement in symptoms, exercise tolerance, or peak flow measurements 4, 5
Consider adding ipratropium for severe symptoms, as the combination of β-agonist with ipratropium is more effective than single-agent therapy in moderate-to-severe exacerbations 4

Consider asthma as a cause of variable airflow obstruction, typically reversible with bronchodilators 2, 1
Consider COPD as a cause of fixed or partially reversible obstruction in patients with smoking history 1
Consider cardiac causes, such as heart failure with pulmonary congestion, which may present with wheezing 6
Avoid assuming all wheezing is asthma or COPD without considering the broad differential diagnosis, and avoid continuing bronchodilator therapy without objective evidence of benefit 5
Avoid using spirometry to screen asymptomatic patients, which leads to overdiagnosis and unnecessary treatment 1, 3