Why Your Specialist Is Checking Your Blood and Your Breath

Before you read — 10 seconds: Is asthma one single condition?

a) Yes b) No

If you have been referred for severe asthma, you may have been asked for a blood test and a breathing test that measures something in the air you breathe out. Both can feel like extra steps when you simply want to breathe better.

They are actually the most important part of the visit.

Asthma is not one condition. It is a group of conditions that look similar from the outside but are driven by different processes on the inside. Two people with identical symptoms can need completely different treatments — and the only way to tell them apart is by measuring.

What the two tests do

The blood test counts eosinophils, a type of white blood cell involved in one common form of airway inflammation. A raised count points toward that pathway and opens the door to treatments designed for it.

The breath test is called FeNO. You breathe out steadily into a device and it measures nitric oxide, which rises when a particular kind of inflammation is present in the airways. It also indicates how well inhaled steroids are working.

Together, these two numbers narrow the options. There are now seven newer treatments for severe asthma, and they work in different ways. Choosing between them is not trial and error — it is guided by what the tests show.

7 newer treatments now exist for severe asthma. Your test results decide which one fits.

Quick check: What does the breath test (FeNO) measure?

a) Lung capacity b) A gas that rises with airway inflammation c) Oxygen levels

Answer: A gas that rises with airway inflammation. It also shows how well inhaled steroids are working.

One thing worth knowing

Prednisone lowers the eosinophil count. If you have been on steroids, your reading may look lower than your true baseline. If you have had a blood test from before you started steroids, mention it. Old results can be genuinely useful.

One more: Can prednisone affect your blood test result?

a) Yes, it lowers the eosinophil count b) No effect

Answer: Yes, it lowers the eosinophil count — which is why a result from before you started steroids is worth mentioning.

What to expect: the blood test is routine. The breath test takes a few minutes, is painless, and involves nothing more than breathing out slowly.

Bring your old results with you

If you have had blood work done before you started steroids, bring it or have it sent over. It can save weeks of repeat testing and help us pick the right treatment sooner.

Call (847) 860-7250.

Never change or stop a medication on your own. Talk to your care team first.

The answer

No. Several different processes can cause similar symptoms, and each one responds to different treatment. That is why the testing matters.

This article is for education only and isn't a substitute for medical care. Questions about your situation? Call the office — we're happy to help.