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Chronic obstructive pulmonary disease - Management
How do I distinguish COPD and asthma?

  • Chronic obstructive pulmonary disease (COPD) and asthma can be difficult to distinguish and may coexist.
  • Compare clinical features.
  • If diagnostic doubt remains, one or more of the following strategies are recommended:
    • Do longitudinal observations of symptoms, peak flow, and/or spirometry.
      • Serial domiciliary peak expiratory flow measurements showing 20% or greater diurnal or day-to-day variability indicate asthma. Peak expiratory flow is not routinely recommended for the diagnosis or assessment of people with COPD, as it may significantly underestimate the degree of airflow obstruction, but it may help to distinguish COPD from asthma.
      • On spirometry, clinically significant COPD is not present if the ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC ratio) increases to 0.7 or greater at follow up. Suspect asthma, in which airways obstruction is variable.
    • Perform reversibility testing using either inhaled bronchodilators or oral prednisolone. The following findings identify asthma:
      • A large (greater than 400 mL FEV1) response to inhaled bronchodilators.
      • A large (greater than 400 mL FEV1) response to 30 mg oral prednisolone given daily for 2 weeks.
    • Start drug treatment and arrange early follow up that includes repeat spirometry. Reconsider the diagnosis of COPD (and suspect asthma) if the person has a marked response to drug treatment, illustrated by either:
      • A marked improvement in symptoms, or
      • Return of FEV1 and the FEV1/FVC ratio to normal.
    • Refer the person to a respiratory specialist for more detailed investigations.

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