Asthma is an inflammatory condition of the airways. Inflammation makes your airways more swollen and sensitive. Reducing inflammation is an important part of treating asthma. Doctors can test for inflammatory biomarkers to understand your asthma better.1,2
An inflammatory biomarker is something a doctor can measure to get an idea of:2,3
- How much inflammation you are experiencing
- How well you may respond to a planned treatment
- How well a current treatment is working for you
We still need more research on the best way to use inflammatory biomarkers.2
What does inflammation have to do with asthma?
Inflammation is an immune response. It can:1
- Swell the lining of your airways
- Cause your body to produce more mucus
- Make your airways more sensitive
This is why anti-inflammatory drugs are an important option for treating asthma.1
Asthma is complex and varies for everyone. We now know that there are more asthma types beyond allergic and nonallergic asthma. For example, the best asthma treatment for you depends on your level of type 2 inflammation.2
Type 2 inflammation is an immune response. It is caused by white blood cells called type 2 T helper cells. When these cells become activated, they release chemical signals that:2
- Increase levels of another type of white blood cell, called eosinophils
- Release a gas called nitric oxide in the airway
- Increase levels of a protein called immunoglobulin E (IgE)
- Release a protein called periostin in the airway
These processes are part of the complex pathways leading to symptoms of asthma. They are also indicators of inflammation. This is why they may be useful to test as inflammatory biomarkers.2
What are inflammatory biomarkers?
Most people with severe asthma have high levels of type 2 inflammation. But not everyone has the same levels. Knowing your level of inflammation can help your doctor suggest the right treatments. It can also help the doctor see if treatments are working. That way, the doctor can fit the treatment plan to you.3
Doctors use biomarkers to assess your level of type 2 inflammation. Biomarkers provide information about health outcomes. They change depending on disease progression or treatment success.3
A few biomarkers indicate type 2 inflammation in asthma. The biomarkers relate to the inflammatory process explained above. These include:2-4
- Eosinophil levels in the sputum (saliva and mucus)
- Eosinophil levels in the blood
- Fraction of exhaled nitric oxide (FeNO)
- IgE levels
How are inflammatory biomarkers used in asthma?
Inflammatory biomarkers are not used to diagnose asthma. They are most useful to predict and monitor responses to treatments. Some of the most common inflammatory biomarkers in asthma include:5
Sputum eosinophil level
Doctors collect sputum samples from mucus coughed up from your lungs. You will inhale a salt spray to draw water into your airways. This makes the mucus thinner and easier to cough up. This process will take about 20 minutes.3,4
A high level of eosinophils in sputum is linked to more severe asthma. High levels also predict a better response to corticosteroid and biologic drugs. Current guidelines recommend using sputum eosinophil levels to adjust treatment for severe asthma. The test requires specialized training and equipment. So it may be hard to find a testing center.5
Blood eosinophil level
Blood samples are easier to collect, and levels of eosinophils in the blood are easy to measure. A high level of eosinophils in the blood increases the risk of severe asthma attacks. High levels also make asthma harder to control.3,4
Blood eosinophil levels can also predict how well you respond to certain treatments. People with higher levels tend to respond better to inhaled corticosteroids and biologics. So your doctor may use this biomarker to predict and track how well these treatments work.3,4
Fraction of exhaled nitric oxide (FeNO)
FeNO is the amount of nitric oxide in your exhaled breath. During the test, you inhale filtered air to fill your lungs. You then exhale into a mouthpiece for 10 seconds. High FeNO levels are linked to:3,4
- More severe asthma
- More sensitive airways
- Asthma attacks
High FeNO levels predict a better response to inhaled corticosteroids and biologics. Current guidelines do not recommend using FeNO to guide treatment for severe asthma. FeNO values can vary greatly from person to person. But doctors may use this measurement along with other biomarkers.5
Blood IgE level
Immunoglobulin E (IgE) levels increase the risk of asthma. Higher levels are linked to allergic asthma, a sensitive airway, and severe asthma. IgE is the target of a biologic treatment called Xolair® (omalizumab). But treatment with Xolair does not seem to affect IgE levels. Other biomarkers must also be used to monitor response to treatments.1,3
Blood periostin level
Periostin is higher in the airways of people with asthma. Higher levels are linked to airway obstruction and poor lung function. High periostin levels may indicate a better response to Xolair. Periostin is not yet used often as a biomarker. We need more research to understand how useful it is.1,3