Chronic lower respiratory diseases, namely, asthma and chronic obstructive pulmonary disease (COPD), are the fifth-leading cause of death in the United States. A contributing factor is diagnostic errors, which can lead to delayed or ineffective treatments and mismanagement.
Telling the difference between these two conditions can be difficult. Not only do they affect broad, diverse populations but also overlapping symptoms and clinical features coupled with a lack of validated screening tools can make diagnosis difficult.
How then, are primary care doctors able to effectively distinguish asthma and COPD, especially given their complexity?
“Asthma and COPD are conditions that present often with very similar symptoms and patients can have them together; they’re both diseases that affect the airways and cause similar patterns on pulmonary function testing,” said Joseph Skalski, MD, head of the asthma section and an assistant professor of medicine at Mayo Clinic in Rochester, Minnesota. “It often comes down to a patient’s clinical history to distinguish the two. But to know what to look at, you need to understand these diseases.”
Square Peg, Round Hole
Many pulmonologists acknowledge the “messiness” of these conditions. Not only can they occur together in the same patient but also “there are many different subtypes in which they show up for patients,” said David Beuther, MD, PhD, professor of medicine, Division of Pulmonary, Critical Care, and Sleep Medicine at National Jewish Health in Denver.
“There’s never going to be a ‘one size fits all,” said Panagis Galiatsatos, MD, associate professor of pulmonary and critical care medicine at Johns Hopkins Medicine in Baltimore.
There are, however, certain distinguishing features that can help clinicians develop a more refined idea, said Beuther. For example, asthma is typically best characterized by its variability and COPD by fixed symptoms.
Where to start? A comprehensive medical history is essential.
Time Travel Is Key
Galiatsatos recommended that primary care physicians take a “time travel” with patients to gain important diagnostic clues.
“Were they premature? Did they have any childhood infections that sent them to the hospital? Were they able to keep up with their peers in sports or during recess?” he said. With female patients, he would try to learn if, during pregnancy, they had experienced any breathing issues, which might point to asthma.
“Then we get into adulthood. I ask patients to tell me when they’re breathless, ie, if it’s when they are on flat surfaces (more indicative of conditioning) or when they are climbing stairs (which might indicate that they’re being robbed of blood flow, and more likely have COPD),
he said. Family history is also important.”
One of the most helpful differences is if the patient has good and bad days (asthma), or constantly live with bad and worse days (COPD), said Galiatsatos, also noting the benefit of the Modified Medical Research Council Dyspnea Scale, which can help classify dyspnea severity in respiratory diseases, especially COPD. Roughly 75% of patients with COPD have also been shown to experience moderate to high chronic cough and/or sputum production.
“The big thing with COPD is the exposure to something that can injure the lungs,” said Mark Yoder, MD, associate professor of medicine, Department of Internal Medicine at Rush University Medical Center in Chicago. “In the United States, that is largely going to be tobacco smoke and certainly, other exposures — mostly occupational — for example, in Chicago where there are large hangers of buses that are warmed up indoors, a bus driver is going to be exposed to high concentrations of diesel fumes.”
Additional occupationally-related exposures include chemicals and fumes that could affect house cleaners, military veterans, firefighters, and others.
Another important consideration is age.
“Almost uniformly, COPD is going to be a disease of patients who are 40 years or older, with the exception of some genetic conditions or maybe some very severe exposures,” said Skalski. “A younger patient with obstruction is likely to have asthma and an older patient with obstruction, COPD. But you can’t distinguish based on age alone,” he emphasized, which is where spirometry can help.
On the other hand, for asthma, “you want to look for clues that support the diagnosis, for example, dermatitis, allergic nose and sinus disease, childhood history, etc.,” said Skalski. “About 60% of cases are going to be eosinophilic asthma, which can be confirmed by laboratory testing for elevated peripheral eosinophil count.”
Spirometry Benefits and Challenges
Data suggest that a medical history that focuses on specific factors such as smoking history, certain respiratory symptoms, and the presence/absence of allergies is a reliable strategy for differentiating asthma and COPD. However, for accuracy, a post bronchodilator spirometry should be conducted.
American Thoracic Guidelines define suspected asthma as a post bronchodilator increase in forced expiratory volume in 1 second (FEV1) > 12% and 200 mL volume, which is consistent with airflow limitation. In COPD, the fixed FEV1/forced vital capacity ratio is low (< 70%) and remains persistently so.
“Spirometry can be done by anybody trained to do it,” said Yoder, “but there are rules that need to be followed to ensure that it’s high quality. And there are definitions of what obstruction is (as well as ways to interpret results) depending on the disease process that you’re talking about.”
“If you have the capability to conduct high quality spirometry where patients perform with maximal effort then go for it,” advised Skalski. Without those criteria, the test is more likely to underestimate a patient’s lung function and sometimes, falsely diagnose COPD or asthma where there is none, he said.
“Several times a week, I will see a patient who had spirometry done locally that showed falsely low values because the test wasn’t performed at maximal effort.”
Instead, it might be easier to send staff to training courses or refer patients to local pulmonary function labs for testing, although, depending on where you are, facilities might be limited in number.
“If there is one point to get out to a primary care audience, it’s that you should never diagnose a patient with COPD (or asthma) without spirometry,” said Skalski. “Other tests, including a chest x-ray, labs, and local eosinophilia can be helpful adjuncts. Just be careful to have a clear diagnosis before starting treatment; inhalers are not benign.”
Skalski, Beuther, Galiatsatos, and Yoder reported no relevant financial relationships.
https://www.medscape.com/viewarticle/it-asthma-or-copd-clinical-pearls-diagnosis-pcps-2025a10008pl
