Looking Beyond Seasonal Triggers: Could Eosinophils Be Driving Your Patients' Severe Asthma?

Frank Trudo, MD, MBA

As many primary care physicians and pulmonologists know all too well, the winter months can be challenging for many of the near 26 million people living with asthma in the US. Whether inside or outside, this time of year presents triggers for asthmatics—from cold air and dry wind, to respiratory viruses, to dust circulating in heating systems, to smoke from wood-burning fires and more—increasing their risk of asthma attacks.

This season can be especially difficult for approximately 2.6 million Americans living with severe asthma, as their attacks can potentially be serious and frequent. But what many people may not know is that if not adequately managed, severe asthma can be debilitating, negatively impacting patients’ lives at home, work, or school, with some asthma attacks that can even be fatal. Even when the season passes, some severe asthma patients may still find themselves suffering from the same symptoms, and many may even be left wondering the cause of their asthma in the first place.

This may be attributed to the decades-old belief by many asthma patients and providers that there is only one type of asthma. However, we're now recognizing that asthma is a heterogeneous disease—there’s not just one type of inflammation driving this disease. In fact, many patients don’t know that their asthma may be caused by something inside of their own body, and according to an analysis of NHANES (National Health and Nutrition Examination Survey) data, 69% of adult patients with asthma had eosinophilic asthma (or e-asthma).*

Eosinophilic asthma is characterized by elevated levels of eosinophils, which are a direct cause of chronic inflammation in severe asthma. Patients with eosinophilic asthma have varying degrees of atopy, ranging from nonatopic to atopic. For eosinophilic asthma patients, immune cells catalyzed by allergic or nonallergic triggers can lead to the production of various signaling molecules called cytokines. The multitude of cytokines produced by these cells can contribute to the recruitment, activation and survival of eosinophils.

Clinical characteristics can help identify an eosinophilic asthma patient; specifically, patients may have eosinophilic asthma if they have elevated levels of blood eosinophils and/or frequent exacerbations (≥2 exacerbations annually), or if ICS at high doses are insufficient to control the disease. Additional clinical characteristics include low FEV₁ with persistent airflow limitation, poor asthma control, allergic rhinitis, normal or moderately elevated immunoglobulin E (IgE), exacerbations improve with systemic steroids, or late-onset asthma.

Since many severe asthma patients may not know they have eosinophilic asthma, they can often continue to follow treatment plans that may not be tailored to their specific type of asthma, and as a result, continue to experience difficulty controlling their symptoms. They also commonly rely on oral corticosteroids (OCS) to help them breathe, despite the potentially serious health risks, such as weight gain, high-blood pressure, risk for fracture, among others.

While OCS can certainly be an important tool in managing asthma in certain cases, frequent OCS use is a signal that a patient’s asthma remains uncontrolled and they may need an updated treatment plan. The issue is that many patients may not be aware that other options exist for them, and without a proper diagnosis, they may continue to follow treatment plans that aren’t tailored to their specific asthma type, resulting in trouble controlling their asthma symptoms.

Beyond symptom control, untreated eosinophilic asthma can also lead to serious consequences, including airway smooth muscle contraction, airway hyperresponsiveness, and airway remodeling. In addition, eosinophilic inflammation can lead to progressive airway damage and poor control.

That’s why it’s important for providers to have regular proactive conversations with their patients—during the winter season and throughout the year—about their asthma triggers and exacerbations to help identify the specific type of asthma that the patient has. Not all asthma is the same, so there is not a one-size-fits all approach to treatment options.

If your patients display any of the clinical characteristics mentioned above, a routine blood test can help diagnose eosinophilic asthma. If your severe asthma patient has elevated eosinophil counts, they might benefit from innovative treatments designed to specifically target eosinophils, a key driver of severe asthma. Understanding these eosinophilic asthma characteristics can be helpful in informing clinical decision-making, and ultimately can help patients to better manage their symptoms.

To learn more, healthcare providers should visit www.eosinophilasthma.com.

Frank Trudo, MD, is a pulmonologist and VP of US Respiratory Medical Affairs at AstraZeneca. The piece reflects his views, not necessarily those of the publication.Healthcare professionals and researchers interested in responding to this piece or contributing to MD Magazine® can reach the editorial staff here.

*Data from the 2005 to 2006 annual survey of a nationally representative sample of a noninstitutionalized United States population in patients with asthma (aged 18-64 years) identified based on the participants’ self-report. Eosinophilic asthma was defined as a blood eosinophil cutoff point of ≥150 cells/μL. Of the 310 adult patients, 69% had a blood eosinophil level ≥150 cells/μL.