COPD and asthma: Diagnostic accuracy requires spirometry
Up to one-third of patients receiving a clinical diagnosis of COPD or asthma have been shown to lack evidence of disease in subsequent lung-function studies.
PRACTICE RECOMMENDATIONS
› Perform spirometry in all patients with symptoms and risk factors suggestive of chronic obstructive pulmonary disease (COPD) or asthma. B
› Consider having a patient use a peak flow meter to support a diagnosis of asthma if spirometry is unavailable. B
› Consider the possibility of a diagnostic error if COPD or asthma is unresponsive to treatment and the initial diagnosis was made without spirometry. B
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
Don’t use in isolation. Use spirometry to support a clinical suspicion of asthma36 or COPD after a thorough history and physical exam, and not in isolation.
Special consideration: Asthma-COPD overlap syndrome
Some patients have features characteristic of both asthma and COPD and are said to have asthma-COPD overlap syndrome (ACOS). Between 15% and 20% of patients with COPD may in fact have ACOS.36 While there is no specific definition of ACOS, GOLD and GINA describe ACOS as persistent airflow limitation with several features usually associated with asthma and several features usually associated with COPD.2,10,37 ACOS becomes more prevalent with advancing age.
In ACOS, patients with COPD present with increased reversibility or patients with asthma and smoking history develop non-fully reversible airway obstruction at an older age.38 Patients with ACOS have worse lung function, more respiratory symptoms, and lower health-related quality of life than individuals with asthma or COPD alone,39,40 leading to more consumption of medical resources.41 In patients with ACOS, the FEV1/FVC ratio is low and consistent with the diagnosis of COPD. The post-bronchodilator response may be variable, depending on the stage of disease and predominant clinical features. It is still unclear whether ACOS is a separate disease entity, a representation of severe asthma that has morphed into COPD, or not a syndrome but simply 2 separate comorbid disease states.
CORRESPONDENCE
Christina D. Wells, MD, University of Illinois Mile Square Health Center, 1220 S. Wood Street, Chicago, IL 60612; cwells2@uic.edu.
