How Can Doctors Tell If It Is Asthma, COPD, or Both?

By John Bottrell, RRT

3 min read

Some people have asthma. Some people have COPD. And some people have both in what is now called Asthma/COPD Overlap Syndrome (ACOS). So, how do doctors differentiate between these three similar but different lung diseases? Here’s what to know.

What are classic strategies?

So, there are many similarities between asthma, COPD, and ACOS. All three may present with similar symptoms. Some treatments are similar too. But, some treatment strategies are unique to the disease. So, doctors will want to get to that accurate diagnosis. So, what are some strategies for doing this?

Guessing: This is the classic way of diagnosing any disease. You present to your doctor with specific symptoms, and your doctor makes an educated guess. Guessing has been used since witch-doctors, seers, and priests were the diagnosers. Sometimes this simple method is still helpful. Surely this is not the ideal way of diagnosing today. But, sometimes it’s all doctors have to work with. For example, you present with symptoms that need to be treated right away. You don’t always have time. So you’re asked a few questions such as, “Do you smoke?” Or, “Is there a history of asthma in your family.” So, sometimes doctors must resort to educated guesses.

Pulmonary Function Testing (PFT): If there’s time, then you ought to have a pulmonary function test (PFT) done. This is where you take a deep breath (“as deep as you can”) and blow into a spirometer (“Keep blowing! Keep blowing! Blow it all out!). You do this before and after using rescue medicine. The results are very revealing. PFTs can show whether you have asthma, COPD, both, or neither.

What are newer strategies?

Interestingly, the new strategies may be the most definitive. All asthmatics and people with COPD have some degree of airway inflammation. Asthmatics tend to have eosinophilic inflammation. This is inflammation caused by specialized white blood cells called eosinophils. COPDers tend to have neutrophilic inflammation. This is inflammation caused by neutrophils.

Two more strategies for diagnosing may include:

Sputum sample: This is a sample of phlegm from deep in your lungs. A sample of phlegm is coughed into a sterile cup. It is then sent to a laboratory. A test determines your sputum eosinophil and neutrophil level. This might be the most accurate strategy for differentiating between asthma and COPD. If your eosinophil level is elevated you have asthma. If your neutrophil level is elevated you have COPD. If both are elevated you have both.¹
Blood sample: This might be the simplest test. All that’s needed is a sample of your blood. It can be drawn with a simple blood sample. The test your doctor orders is a complete blood count (CBC). The blood is sent to a lab. Your eosinophil and neutrophil levels are determined. Again, if your eosinophil level is elevated you have asthma. If your neutrophil level is elevated you have COPD. If both are elevated you have both.²

What is the best strategy?

A CBC to diagnose asthma and COPD is not standard yet. However, a recent study shows it may prove useful. It’s more accurate than making an educated guess. It’s also more convenient than doing a PFT or spitting up phlegm.

A recent study showed how this might work. Researchers followed 195 patients. This was between July 2015 and November 2017. They all had their blood drawn for a CBC. Researchers examined the eosinophil and neutrophil levels. So, here are the results.²

Asthma: Eosinophils elevated (17.4%) and Neutrophils were not elevated (78.8%)
COPD: Eosinophils were not elevated (1.8%) and Neutrophils elevated (95.6%)ACOS. Eosinophils elevated (11.8%) and Neutrophils elevated (84.2%)²

What’s important here is that these levels correlated with sputum eosinophil and neutrophil levels. This was true both between flare-ups and during flare-ups. This shows doctors wouldn’t have to necessarily obtain a sputum sample. They could just draw your blood.

A summary of tests

A PFT is the most accurate test to diagnose asthma, COPD, and ACOS. But, it usually takes time. It's a lot of work for people who otherwise have trouble breathing. It would be unreasonable to ask someone to do this during an exacerbation. So, when a quick diagnosis is necessary, doctors often resort to other methods of diagnosing. In the past, this left doctors no choice but to make an educated guess. Today, doctors have the option of obtaining a sputum sample. In the near future, a CBC may be a standard test ordered when someone presents with asthma or COPD-like symptoms.

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The COPD.net team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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Leon Lebowitz, RRT Member
Another excellent article with valuable information, John. This will be extremely helpful for us to refer to when citing references. Thanks so much for having it published! Leon (site moderator)
deirdreeeast Member
Explained the pathology and appropriate treatment in basic terminology
1. John Bottrell, RRT Moderator & Contributor
 Thanks so much. Glad you enjoyed the article. Wishing you all the best. John. Author/ <a href='https://Asthma.net' target='_blank' rel='noopener noreferrer ugc'>Asthma.net</a> Site Moderator.
ac42901 Member
Had CBC done last month. Eosonophils and neutrophils are both at the lower end of normal ranges, yet I was diagnosed stage 2 COPD three years ago. Have SOB climbing stairs, that's about it.
1. Leon Lebowitz, RRT Member
 Hi ac42901 and thanks for joining in the conversation here. It sounds like you have been diagnosed with both asthma and COPD, from what you've shared here with the community. In view of your post, I thought you might find it both interesting and informative to look over this article on the early stages of COPD: <a href='https://copd.net/living/early-stage-treatment' target='_blank'>https://copd.net/living/early-stage-treatment/</a>. I do hope you also find it to be helpful. All the best, Leon (site moderator)
johnb Member
I find this article very interesting. My Doctors Practice sends for me once a year for an Asthma and COPD clinic. All it consists of these days is a few questions about how I am. No Spirometry. No tests at all. When I go next time I will quote this articel and I know what the reaction will be. Total dismissal of it. 
1. John Bottrell, RRT Moderator & Contributor
 <inline-mention username="johnb" user-id="2466373"/>. Hi again. I really like your question about your full blood count. This is the kind of question that I like to ask my own doctor. I think this question, worded just as you did above, would be a great one to pose to your own personal physician. If you have access to your doctor's email, this may be a good one to email your doctor. What do you think? I am curious to hear what your doctor says. John. <a href='https://copd.net' target='_blank'>copd.net</a> community moderator. 
2. johnb Member
 <inline-mention username="John Bottrell, RRT" user-id="2438001"/> My Doctor is just a normal GP. I have had asthma since I was 2. It was a few years back when a Consultant at a local hospital told me I had COPD as well as Asthma. All I see these days is a practice nurse. Quite honestly. I dont see the point in going. All she does is ask me how I am.
njb Member
This is very helpful information, thank you so much!
1. John Bottrell, RRT Moderator & Contributor
 <inline-mention username="njb" user-id="2401198"/> Thank you! I appreciate your kindness. Wishing you all the best. John. author and <a href='https://copd.net' target='_blank'>copd.net</a> community moderator.