What Is Eosinophilic Asthma (E-Asthma)?

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Eosinophilic asthma, also known as e-asthma, is one of the most common subtypes of asthma diagnosed in adulthood. Eosinophilic asthma is defined as asthma with an elevated eosinophil count of at least 150 cells per μL. Allergic asthma is not the same as eosinophilic asthma. Eosinophilic asthma is classified as atopic, which means that there is a genetic tendency for allergies to be the cause of disease.

Inflammation from eosinophilic asthma occurs as part of an allergic or immune system response, which releases a specific white blood cell called eosinophils. When you have an increase in white blood cells, you will typically have an inflammatory response, which leads to thickening of your airways. The fluid and mucus that results may lead to spasms in your airways (bronchioles) and cause your asthma symptoms.

Prevalence

Asthma is an inflammatory disorder of your airways that can make it difficult to breathe. About 1 of 13 people suffer from this chronic illness, and almost half of the people affected by asthma have an asthma attack each year.

Know that most of these exacerbations are preventable if the asthma is properly managed. While originally thought to be a single disorder, asthma actually has many subtypes that can alter how your asthma can best be controlled.

About 5% to 10% of people with asthma have severe asthma. While the prevalence of having eosinophilic asthma is relatively unknown, studies suggest that around 50% percent of cases of severe asthma are eosinophilic asthma.

If you are older than 35 when you are diagnosed with severe asthma you have a higher risk of being diagnosed with eosinophilic asthma. Your risk is the same regardless of your gender, and you have a lower risk of being diagnosed with eosinophilic asthma in your childhood and teenage years.

Symptoms

Many of the symptoms of eosinophilic asthma are the same as other forms of asthma including:

There are a few symptoms that may also be present that are not typically associated with asthma including:

While eosinophilic asthma is an immune response related to allergies, many people diagnosed with it do not suffer from allergies such as molds, mildews, or other common allergens.

Diagnosis

Eosinophilic asthma is often under-diagnosed. It is not considered common even though the prevalence is thought to be higher than previously believed.

If eosinophilic asthma is the cause of your asthma and is not diagnosed, you may struggle to get your severe asthma under control.

You generally want to be seen by a pulmonologist if you are concerned. Allergists and immunologists may also be helpful in your thorough evaluation.

Eosinophil Cell Count

Performing a cell count of eosinophils from an induced sputum sample is considered the gold standard measure of inflammatory cell counts, but it is difficult to obtain, time-consuming, and observer-dependent. It often requires the use of a specific lab staffed with experts.

When collecting the specimen, you want to ensure that you are not spitting saliva, but coughing up sputum from your airways. The coughed up specimen can then be analyzed in a lab to see if the sputum eosinophil count is equal to or great than 3%.

To help induce sputum, your doctor or a respiratory therapist may give you a dose of salbutamol or another fast-acting bronchodilator. This treatment is then followed by giving you a nebulized hypertonic saline. The higher concentration of saline when inhaled irritates the airways and helps to induce coughing.

Airway Biopsy

Another way to determine whether you have e-asthma is with an airway biopsy, which is performed during a bronchoscopy. This procedure can be used to identify abnormal cells in the diagnosis of several different lung diseases.

However, this method is not recommended as the first step in identifying eosinophilic asthma unless a sufficient sputum sample can't be obtained since it is an invasive procedure that requires some sedation.

Other Methods

Other methods have been developed to help diagnose e-asthma. Your physician may check a complete blood count (CBC) to check for eosinophilia (increased eosinophil count).

A careful interpretation of your blood eosinophils will be considered by your physician since elevated counts in your blood do not guarantee that you have eosinophilic asthma. That said, it may help your physician in further differentiating any other symptoms you are having.

Other diagnoses that may be considered if you have an elevated eosinophil count in your blood include hypereosinophilic syndrome, autoimmune disorders, adrenal insufficiency, and medication reactions.

Two additional tests may be considered as a surrogate to an induced sputum or blood eosinophil count: a fractional exhaled nitric oxide (FeNO) breathing test and the periostin blood test. If you have eosinophilic asthma, you will typically show increased eosinophils in your blood and sputum, immunoglobulin E, FeNO, and periostin.

FeNO can be useful in helping to predict if your condition will improve with inhaled corticosteroids. The test can be done using a device called NIOX. However, many factors can affect your levels of FeNO including the use of steroids, age, sex, atopy (tendency to develop allergies), and smoking status.

Periostin is a biomarker in your airway epithelial cells. Periostin levels tend to be elevated in asthma that activates certain immune cells (TH2) and in some studies has been shown to be an excellent surrogate for testing sputum.

But results are variable in other studies and the test is not easily available. Induced sputum and blood eosinophil counts are still preferable to FeNO and periostin according to most clinicians and guidelines.

Treatment

First-line treatment of eosinophilic asthma should include your standard asthma treatment regimen. Often you will experience good results from inhaled corticosteroids (ICS) that are used as part of the standard asthma treatment guidelines.

If your doctor has diagnosed you with eosinophilic asthma, they may alter the standard approach used with corticosteroids. Corticosteroid medications include:

  • QVAR (beclomethasone proprionate HFA)
  • Pulmicort (budesonide)
  • Flovent (fluticasone proprionate)
  • Asmanex (mometasone)
  • Azmacort (triamcinolone acetonide)

While inhaled corticosteroids often have beneficial effects, some people have steroid-refractory eosinophilic asthma, which simply means that your asthma does not have symptomatic or clinical benefit from taking inhaled corticosteroids.

If you have tried one or more of the inhaled corticosteroids listed above without symptomatic relief, then you will want to discuss with your doctor some of the more recently discovered medications that are used to treat eosinophilic asthma.

There are five targeted therapies that have received approval from the U.S. Food and Drug Administration (FDA) for treatment of allergic asthma:

  • Xolair (omalizumab), an anti-immunogobulin E (IgE) class medication
  • Nucala (mepolizumab), formerly known as Bosatria, an anti-interleukin-5 (IL5) class medication
  • Cinqair (reslizumab), another anti-IL5 class medication
  • Fasenra (benralizumab), an anti-IL5 class medication
  • Dupixent (dupilumab), indicated for severe eosinophilic asthma

The five medications listed above have shown favorable results if you are still symptomatic despite good adherence to your prescribed corticosteroid regimen. Of these, omalizumab tends to be the least successful, as it affects allergies more specifically than mepolizumab and reslizumab.

These medications are also generally well tolerated with minimal side-effects with the likelihood that you will also be able to decrease your use of corticosteroids. Minimizing use of steroids also brings a reduction in side effects that can increase your quality of life.

Monitoring

Follow-up is recommended as targeted therapies are not a cure, but a treatment. Be prepared for periodic testing and to discuss the following with your physician at follow-up appointments:

  • Pulmonary function testing
  • Symptoms experienced since last visit (improved or worsening)
  • The frequency of asthma exacerbations
  • Resolution of complications like loss of smell
  • Overall health status
  • Tracking of Quality of Life surveys
  • Laboratory analysis

A standard follow-up appointment is about two to six weeks after starting a new medication. If you have experienced positive results, you will continue on the medication prescribed and follow up in one to six months. If you need to get off the medication, appointments should be made at three-month intervals.

A Word From Verywell

While eosinophilic asthma is associated with severe asthma, treatment is possible if diagnosed properly. Untreated eosinophilic asthma will likely result in difficulty controlling asthma exacerbations—which not only worsens your quality of life but can be life-threatening. Working with your pulmonologist with targeted therapies can help you get back the quality of life that you deserve and may reduce the frequency of your asthma exacerbations.

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