Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 23 peer-reviewed journal articles Updated
Pulmonology

Monitoring, Biomarkers & What to Expect: Tracking Your Asthma

At a Glance

Doctors track severe eosinophilic asthma by monitoring biomarkers like blood eosinophil counts and exhaled nitric oxide (FeNO). By managing these inflammatory markers with targeted treatments, patients can work toward clinical remission, meaning no severe attacks or daily steroids for a full year.

Managing severe asthma is no longer just about reacting to attacks; it is about tracking the invisible “fire” inside your airways to prevent those attacks from happening in the first place. By monitoring specific biomarkers—biological signs of inflammation—you and your care team can adjust your treatment with precision. [1][2]

Your Biological “Dashboard”

There are two primary markers your doctor will use to monitor your eosinophilic asthma. Think of these as the gauges on a dashboard that tell you how much inflammation is present.

  • Blood Eosinophil Count (BEC): This is a simple blood test that measures the number of eosinophils circulating in your body. [3]
    • The Thresholds: A count of 150 to 300 cells/μL or higher is often the “cutoff” that tells doctors your asthma is driven by Type 2 inflammation. [4][5]
    • The Masking Effect: It is important to know that oral steroids (like prednisone) can artificially lower this number, potentially hiding the true severity of your inflammation. [6][7]
  • FeNO (Fractional Exhaled Nitric Oxide): This test involves breathing into a hand-held device. It measures nitric oxide, a gas produced by the cells in your lungs when they are inflamed. [8]
    • What it means: A FeNO level of 20 ppb or higher suggests the presence of Type 2 inflammation. However, levels above 50 ppb are generally considered “high” and indicate that your lungs are significantly inflamed. [9][10]
    • Tracking Adherence: FeNO is also a great way to see if your inhaled steroids are reaching the right spots. If your FeNO remains high despite regular inhaler use, it may signal that your asthma is resistant to standard steroids. [11][12]

The New Goal: Clinical Remission

For a long time, the goal of asthma treatment was simply “control”—having fewer symptoms. Today, with the arrival of advanced biologics, experts have set a more ambitious “gold standard” called clinical remission. [13][14]

While definitions are still being refined, most experts agree that clinical remission means you have achieved all of the following for at least 12 months: [15][16]

  1. Zero Exacerbations: No asthma attacks that require emergency care or “rescue” steroids. [17]
  2. No Maintenance Oral Steroids: You have successfully tapered off daily prednisone or other oral corticosteroids. [18]
  3. Stable Lung Function: Your breathing tests (like FEV1, which measures how much air you can forcefully exhale in one second) remain steady and close to normal. [15]
  4. Minimal Symptoms: You rarely need your rescue inhaler and can go about your daily life without asthma holding you back. [17]

What to Expect Long-Term

As you move into long-term management, your monitoring will become a routine part of your health journey.

  • Routine Check-ups: Most patients on biologics see their specialist every 3 to 6 months to check their BEC and FeNO levels and ensure the medication is still doing its job. [5]
  • The Dupilumab “Spike”: If you are prescribed dupilumab, don’t be alarmed if your blood eosinophil count goes up temporarily when you first start. [19] This is a known phenomenon where eosinophils move out of your lung tissue and into the blood before eventually clearing out. [20] This spike is usually harmless and doesn’t mean the drug isn’t working. [21]
  • Patience is Key: Achieving clinical remission is a marathon, not a sprint. It can take several months for your biomarkers to stabilize and for your lungs to begin healing. [4][22] Your doctor will look at the “big picture” of your results over time rather than reacting to a single high number. [23]

Common questions in this guide

What does a high blood eosinophil count mean for my asthma?
A blood eosinophil count of 150 to 300 cells/μL or higher typically indicates that your asthma is driven by Type 2 inflammation. Tracking this number helps your care team determine the severity of your inflammation and whether targeted biologic therapies are working.
What is a FeNO test and why is it used for asthma?
A FeNO test measures the amount of nitric oxide in your exhaled breath, which serves as an indicator of airway inflammation. A result of 20 ppb or higher suggests Type 2 inflammation, allowing doctors to monitor if your daily inhalers are effectively reaching your lungs.
What is clinical remission in severe asthma?
Clinical remission means you have gone at least 12 months with no severe asthma attacks, no need for daily oral steroids, stable lung function, and minimal daily symptoms. With the introduction of advanced biologic medications, this is the new standard goal for long-term asthma care.
Why did my eosinophil count go up after starting dupilumab?
It is common to experience a temporary spike in blood eosinophil counts when first starting dupilumab. This happens because the medication pushes eosinophils out of your inflamed lung tissue and into your bloodstream before they eventually clear out, which is usually harmless.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is my target FeNO level, and how often will we measure it to ensure my inhalers are working effectively?
  2. 2.Can we review my blood eosinophil counts over the last year to see if they are trending down as expected with my biologic therapy?
  3. 3.Since I'm on dupilumab, should we be concerned about any transient increases in my eosinophil levels, and what specific symptoms would indicate a problem?
  4. 4.Based on my current symptoms and lung function, how close am I to meeting the criteria for 'clinical remission'?
  5. 5.If my FeNO stays high even though I'm using my inhaler correctly, what are our next steps for investigating corticosteroid resistance?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

Related questions

Can Wildfire Smoke Stop Asthma Biologics from Working?Do Fasenra or Nucala Protect Against Wildfire Smoke?What If Your Rescue Inhaler Fails During Wildfire Smoke?Why Does Wildfire Smoke Cause a Delayed Asthma Flare-Up?

References

References (23)
  1. 1

    Characteristics, phenotypes, mechanisms and management of severe asthma.

    Chung KF, Dixey P, Abubakar-Waziri H, et al.

    Chinese medical journal 2022; (135(10)):1141-1155 doi:10.1097/CM9.0000000000001990.

    PMID: 35633594
  2. 2

    Defining type 2 asthma and patients eligible for dupilumab in Italy: a biomarker-based analysis.

    Canonica GW, Blasi F, Crimi N, et al.

    Clinical and molecular allergy : CMA 2021; (19(1)):5 doi:10.1186/s12948-021-00146-9.

    PMID: 34020658
  3. 3

    The Combined Value of Type2 Inflammatory Markers in Chronic Obstructive Pulmonary Disease.

    Liu Y, Ma G, Mou Y, et al.

    Journal of clinical medicine 2022; (11(10)) doi:10.3390/jcm11102791.

    PMID: 35628917
  4. 4

    Dupilumab Is Effective in Patients With Moderate-to-Severe Uncontrolled GINA-Defined Type 2 Asthma Irrespective of an Allergic Asthma Phenotype.

    Rabe KF, FitzGerald JM, Bateman ED, et al.

    The journal of allergy and clinical immunology. In practice 2022; (10(11)):2916-2924.e4 doi:10.1016/j.jaip.2022.06.036.

    PMID: 36028446
  5. 5

    Management of severe asthma: a European Respiratory Society/American Thoracic Society guideline.

    Holguin F, Cardet JC, Chung KF, et al.

    The European respiratory journal 2020; (55(1)) doi:10.1183/13993003.00588-2019.

    PMID: 31558662
  6. 6

    Biomarker profile and disease burden associated with intermittent and long-term oral corticosteroid use in patients with severe asthma prior to biologic initiation in real-life (STAR).

    Schleich F, Larenas-Linnemann D, Altraja A, et al.

    The World Allergy Organization journal 2025; (18(7)):101066 doi:10.1016/j.waojou.2025.101066.

    PMID: 40524942
  7. 7

    Clinical evaluation of type 2 disease status in a real-world population of difficult to manage asthma using historic electronic healthcare records of blood eosinophil counts.

    Azim A, Newell C, Barber C, et al.

    Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology 2021; (51(6)):811-820 doi:10.1111/cea.13841.

    PMID: 33528864
  8. 8

    Simultaneously increased fraction of exhaled nitric oxide levels and blood eosinophil counts relate to increased asthma morbidity.

    Malinovschi A, Janson C, Borres M, Alving K

    The Journal of allergy and clinical immunology 2016; (138(5)):1301-1308.e2 doi:10.1016/j.jaci.2016.01.044.

    PMID: 27113848
  9. 9

    Baseline FeNO as a prognostic biomarker for subsequent severe asthma exacerbations in patients with uncontrolled, moderate-to-severe asthma receiving placebo in the LIBERTY ASTHMA QUEST study: a post-hoc analysis.

    Busse WW, Wenzel SE, Casale TB, et al.

    The Lancet. Respiratory medicine 2021; (9(10)):1165-1173 doi:10.1016/S2213-2600(21)00124-7.

    PMID: 34181876
  10. 10

    Treatment Resistance in Severe Asthma Patients With a Combination of High Fraction of Exhaled Nitric Oxide and Low Blood Eosinophil Counts.

    Hoshino Y, Soma T, Uchida Y, et al.

    Frontiers in pharmacology 2022; (13()):836635 doi:10.3389/fphar.2022.836635.

    PMID: 35517829
  11. 11

    Remotely Monitored Therapy and Nitric Oxide Suppression Identifies Nonadherence in Severe Asthma.

    Heaney LG, Busby J, Bradding P, et al.

    American journal of respiratory and critical care medicine 2019; (199(4)):454-464 doi:10.1164/rccm.201806-1182OC.

    PMID: 30339770
  12. 12

    Fractional exhaled nitric oxide and asthma treatment adherence.

    Butler CA, Heaney LG

    Current opinion in allergy and clinical immunology 2021; (21(1)):59-64 doi:10.1097/ACI.0000000000000704.

    PMID: 33369570
  13. 13

    Modifying the course of asthma: mechanisms and strategies for clinical remission.

    Bondi B, Bagnasco D, Braido F

    Current opinion in allergy and clinical immunology 2026; (26(1)):52-58 doi:10.1097/ACI.0000000000001129.

    PMID: 41330485
  14. 14

    The Relationship of Asthma Biologics to Remission for Asthma.

    Menzies-Gow A, Szefler SJ, Busse WW

    The journal of allergy and clinical immunology. In practice 2021; (9(3)):1090-1098 doi:10.1016/j.jaip.2020.10.035.

    PMID: 33130146
  15. 15

    Contribution of the Remission Concept to the Treatment of Asthma.

    Pérez-de-Llano L, Veiga-Teijeiro I, Dacal-Rivas D

    Archivos de bronconeumologia 2023; (59(9)):550-551 doi:10.1016/j.arbres.2023.03.009.

    PMID: 37005151
  16. 16

    A real-world study to evaluate effectiveness of mepolizumab in treating severe asthma in Taiwan (REMIT).

    Cheng SL, Lin SM, Peng CK, et al.

    Therapeutic advances in respiratory disease 2025; (19()):17534666241308406 doi:10.1177/17534666241308406.

    PMID: 39829048
  17. 17

    Long-term effects of mepolizumab in patients with severe eosinophilic asthma: a 6-year real-life experience.

    Stanziola AA, Candia C, Nazzaro G, et al.

    Frontiers in pharmacology 2024; (15()):1449220 doi:10.3389/fphar.2024.1449220.

    PMID: 39175541
  18. 18

    Comparison of clinical remission criteria for severe asthma patients receiving biologic therapy.

    Breslavsky A, Al Qaied A, Tsenter P, et al.

    Respiratory medicine 2024; (222()):107528 doi:10.1016/j.rmed.2024.107528.

    PMID: 38199287
  19. 19

    Profiling Blood Hypereosinophilia in Patients on Dupilumab Treatment for Respiratory Conditions: A Real-Life Snapshot.

    Caminati M, Maule M, Bagnasco D, et al.

    The journal of allergy and clinical immunology. In practice 2025; (13(6)):1367-1374.e4 doi:10.1016/j.jaip.2025.01.040.

    PMID: 39956163
  20. 20

    Eosinophilia and Adverse Effects of Dupilumab for Respiratory Indications: A Real-World Setting.

    Li SH, Nehme KF, Moshkovich A, et al.

    The journal of allergy and clinical immunology. In practice 2025; (13(1)):121-131 doi:10.1016/j.jaip.2024.09.013.

    PMID: 39322036
  21. 21

    Dupilumab-induced hypereosinophilia: review of the literature and algorithm proposal for clinical management.

    Caminati M, Olivieri B, Dama A, et al.

    Expert review of respiratory medicine 2022; (16(7)):713-721 doi:10.1080/17476348.2022.2090342.

    PMID: 35703018
  22. 22

    Clinical Remission Criteria and Serum Levels of Type 2 Inflammation Mediators during 24 Weeks of Treatment with the Anti-IL-5 Drug Mepolizumab in Patients with T2-High Severe Asthma.

    Palacionyte J, Januskevicius A, Vasyle E, et al.

    Diagnostics (Basel, Switzerland) 2024; (14(13)) doi:10.3390/diagnostics14131345.

    PMID: 39001236
  23. 23

    Effective Management of Severe Asthma with Biologic Medications in Adult Patients: A Literature Review and International Expert Opinion.

    Buhl R, Bel E, Bourdin A, et al.

    The journal of allergy and clinical immunology. In practice 2022; (10(2)):422-432 doi:10.1016/j.jaip.2021.10.059.

    PMID: 34763123

This page explains biomarkers and monitoring for eosinophilic asthma for educational purposes only. Always consult your pulmonologist or allergist for help interpreting your specific test results and treatment plan.

Get notified when new evidence is published on Severe Refractory Eosinophilic Asthma.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.