When it comes to respiratory allergies, the role of eosinophils can be perplexing. But understanding how eosinophilic inflammation affects the immune response is essential in providing effective treatment for allergy sufferers. In this post, I’ll examine the science behind eosinophils and their influenza-like symptoms, as well as discuss how doctors might use medication and other strategies to effectively alleviate these uncomfortable episodes. With a better grasp on what’s going on inside an allergic patient’s body, both doctors and patients will have deeper insight into treating airway swelling and irritation that often results from airborne allergens like pollen or dust mites.

I can remember 10 years ago, none of us as allergists, even looked for the level of eosinophils in the peripheral blood! Why was that even necessary as the eosinophil level didn’t change what treatment we recommended. In fact, medical researchers at our annual allergy meetings said the eosinophil could be blocked, but it only applied to a few patients. Even how we calculate the total number of eosinophils in peripheral blood has changed over the past 10 years. You must calculate the eosinophil count by multiplying the total WBC count x the % of eosinophils on the smear. Sorry, you can’t rely on the “pre calculated” value or you’ll underestimate the value. As an example, if WBC count is 6,500 and eos % is 4.5 the correct calculation is 6500 x 0.045 (converting percentage to decimal) or 292. Eosinophil counts should be < 30, so you can see this count should cause some concern. Hopefully, this will give you some background information about what’s normal in the eosinophil world before a very intense drill down of data suggesting that the eosinophil is responsible for many respiratory conditions.

September 30, 2021

From PulmonologyAdvisor: https://www.pulmonologyadvisor.com/home/topics/copd/the-role-of-peripheral-eosinophil-counts-in-identifying-copd-subtype/

The Role of Peripheral Eosinophil Counts in Identifying COPD Subtype

Brandon May Follow @@brandonmilesmay

Elevated peripheral eosinophil counts may be a useful indicator for identifying patients with chronic obstructive pulmonary disease (COPD) and eosinophilic inflammation, irrespective of asthma history, according to research findings published in the journal Thorax.

Researchers sought to determine the prevalence of eosinophilic inflammation among individuals with COPD by analyzing elevated fractional exhaled nitric oxide (FeNO) levels and peripheral eosinophil counts. The analysis was based on National Health and Nutrition Examination Survey data from 2007 to 2010 for 3,110,617 patients (mean age, 59.3 years; 64.4% male) with COPD. All patients were age 40 or older and had a postbronchodilator forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) ratio less than 0.70.

Within the entire COPD cohort, 14.6% of patients had a history of asthma. The prevalence of asthma (vs no asthma) was highest among women (58.3% vs 31.7%, respectively; P <.001) and among those who were non-Hispanic and Black (6.2% vs 4.4%; P <.001) or non-White, non-Hispanic individuals of other races/ethnicities (11.4% vs 5.4%; P <.001).

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While the overall prevalence of peripheral eosinophilia was 36%, the prevalence was significantly higher among patients with COPD and an asthma history vs. those with COPD and no asthma history (38.3% vs 35.5%; P <.001). Additionally, while 14.3% of the entire cohort had an elevated FeNO (of ≥25 ppb), elevated FeNO was higher among patients who had COPD and an asthma history (28.7%), compared with those who had COPD but no asthma history (15.2%).

In distinguishing patients with COPD and FeNO levels of at least 25 ppb from patients with FeNO levels less than 25 ppb, the researchers found that the sensitivities of peripheral eosinophil count thresholds of 100 cells/μL, 200 cells/μL, and 300 cells/μL were 90%, 50% and 33%, respectively, while specificities were 40%, 72%, and 90% (area under the curve, 0.70; 95% CI, 0.61-0.80).

A limitation of the study, researchers noted, was the fact that the NHANES data used were subject to both sampling and non-sampling errors, and that the asthma self-reports used were subject to recall bias.

The researchers concluded, “Elevated peripheral eosinophil counts have a good sensitivity and specificity in identifying COPD subjects with eosinophilic inflammation with or without a reported history of asthma.”

Reference

Annangi S, Nutalapati S, Sturgill J, Flenaugh E, Foreman M. Eosinophilia and fractional exhaled nitric oxide levels in chronic obstructive lung disease. Thorax. Published online August 20, 2021. doi:10.1136/thoraxjnl-2020-214644

Ok, so what does this study really mean from a practical standpoint?

• All patients with respiratory illness such as coughing, wheezing, asthma should have their eosinophil counts calculated like I’ve demonstrated for you to get the “real” number of eosinophils in the blood. If the counts are elevated and you’ve already tried the standard asthma medications such as inhaled corticosteroids, your patient may be a candidate for biological therapy.
• What is biological therapy? I’m glad you asked! Biologicals remove the eosinophil or the driving factor (IL-5) and bring these levels down to normal. And the best thing? No steroids are involved. That’s pretty cool and patients really dig this idea.
• Here’s some examples of brands of biologicals that can do this amazing transformation–Nucala, Fasenra, Dupixent, Cinqair–which one is better? Depends on what you’ve tried before and which drug rep has last brought you lunch 🙂
• Xolair blocks IgE (not the eosinophil), but works in the same way by reducing inflammation without oral steroids.
• Biologics also offer a convenient dosing schedule of every 2-8 weeks; at least it isn’t every day or you strike out. This makes a big difference with compliance and it appears the optimal interval between dosing may be every month. Patients remember monthly intervals and will at least tell you when they have missed a dose.
• What if you have asthma, but your IgE and eosinophil counts are low–you know, the doctor didn’t find anything! There is hope for you as well. Tezspire blocks another messenger called TSLP and doesn’t require IgE/eosinophils to be elevated in order to work for your asthma.

If you have asthma and your eosinophil levels are high, it is important to see an allergy specialist. They will be able to calculate your eosinophil count and give you the best course of treatment. Biologics can block the function of eosinophils and thus improve asthma without oral steroids, but they should only be used under medical supervision. Even if your eosinophil counts aren’t elevated, we have biologics in our arsenal that can provide relief. So, if you think biologicals may be right for you, don’t hesitate to contact us today. Our phone number at Warren Clinic Allergy is (918)-495-2636.