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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Pulmonology

Testing and the New Diagnostic Standards

At a Glance

Under the 2024 ISHAM criteria, ABPA is usually diagnosed with asthma, cystic fibrosis, bronchiectasis, or COPD, positive Aspergillus-specific IgE and usually high total IgE, plus at least two supportive findings such as high eosinophils or characteristic CT changes. Steroids and biologics can alter results.

Because the symptoms of Allergic Bronchopulmonary Aspergillosis (ABPA) so closely resemble severe asthma or cystic fibrosis, doctors rely on a specific combination of blood tests and imaging to confirm the diagnosis. In 2024, the International Society for Human and Animal Mycology (ISHAM) updated the official criteria to help doctors catch cases more accurately and earlier [1][2].

The 2024 ISHAM Diagnostic Framework

To be diagnosed with ABPA under the 2024 guidelines, you are usually associated with a “predisposing condition”—most commonly asthma, cystic fibrosis, chronic bronchiectasis, or COPD [1][2]. If you have one of those, your doctor looks for two “essential” markers and then at least two “supportive” markers [1].

Essential Markers (Both must be present)

  1. Aspergillus-specific IgE: A blood test showing you are “sensitized” to the mold. The threshold is usually ≥ 0.35 kUA/L [1][3].
  2. Total Serum IgE: A measure of your overall allergic “volume.” This is generally ≥ 500 IU/mL [1][3]. (Note: A lower value does not definitively rule out ABPA, especially if you have recently taken oral corticosteroids or if other clinical findings strongly support the diagnosis).

Supportive Markers (At least 2 must be present)

  • Aspergillus-specific IgG: An antibody that shows a more chronic immune response. Cutoffs vary by the specific lab assay used [1][3].
  • Blood Eosinophils: A type of white blood cell involved in allergic inflammation. The historical threshold is ≥ 500 cells/µL [1][3].
  • Suggestive Imaging: Findings on a CT scan that are characteristic of ABPA [1].

Understanding Your Lab Results and Medications

Your blood work measures how your immune system is reacting to the Aspergillus fungus. It is important to know that these numbers can change if you are already taking steroids or certain “biologic” medications. Do not interpret the cutoffs on your own without your clinician’s context [4][5].

  • Total IgE: Think of this as your immune system’s allergic activity. While a high number is a key piece of the puzzle, if you are taking the biologic omalizumab (Xolair), it actually increases your measured Total IgE on blood tests because it binds to the IgE in your blood [6][7].
  • Eosinophils: These cells swarm your lungs during an ABPA flare. High levels indicate active allergic inflammation. However, systemic steroids and certain biologics (like mepolizumab or benralizumab) suppress eosinophils. A normal eosinophil count does not mean you do not have ABPA [8].

What the CT Scan Looks For

Doctors use High-Resolution CT (HRCT) to look deep into the airways for damage or blockage. Common findings include bronchiectasis (widened, scarred airways) and mucus plugging [2][9].

High-Attenuation Mucus (HAM): A “Signature” Finding

One of the most important things a radiologist looks for in suspected ABPA is High-Attenuation Mucus (HAM) [10].

  • What it is: In many people with ABPA, the mucus in their lungs becomes very thick and contains minerals or fungal debris. On a CT scan, this mucus looks “denser” (brighter) than the surrounding muscle [10][11].
  • Why it matters: HAM is incredibly specific to ABPA in the right clinical context (such as in cystic fibrosis) [12]. While not everyone with ABPA has HAM, its presence is a very strong indicator that your immune system is reacting to the fungus, though it does not replace the full clinical evaluation [13][10].

The Importance of the “Fleeting” Shadow

You may see the term fleeting opacities on your radiology report [14]. These are shadows caused by mucus and inflammation that seem to “wander”—appearing in one part of the lung on one scan and moving to a different spot or disappearing entirely on the next [15][16]. This “moving” nature is a classic sign of the mucus plugging seen in ABPA, rather than a permanent scar [17].

Common questions in this guide

What blood tests are used to diagnose ABPA under the 2024 ISHAM criteria?
The two essential blood tests are Aspergillus-specific IgE, usually at least 0.35 kUA/L, and total serum IgE, generally at least 500 IU/mL. The diagnosis also usually requires at least two supportive findings, such as Aspergillus-specific IgG, a high eosinophil count, or characteristic CT findings.
Can steroids or biologic medicines change my ABPA test results?
Yes. Oral or systemic corticosteroids can lower some measured immune signals, and medicines such as mepolizumab or benralizumab can suppress eosinophil counts. Omalizumab can increase the total IgE measured in blood, so your clinician should interpret results alongside your medications.
What does high-attenuation mucus on a CT scan mean in ABPA?
High-attenuation mucus is unusually dense mucus in the airways that may contain minerals or fungal debris. In the right clinical setting, it is a strong indicator of ABPA, but it does not replace the complete evaluation of symptoms, blood tests, and imaging.
What do bronchiectasis and mucus plugging mean on an ABPA CT report?
Bronchiectasis means that some airways have become widened or damaged, while mucus plugging means thick mucus is blocking the airways. Both findings can occur in ABPA and help clinicians assess whether the CT pattern supports the diagnosis.
Can a normal eosinophil count or lower IgE rule out ABPA?
No. Steroids and some biologic medicines can lower eosinophil counts, and a lower total IgE level can occur after corticosteroid treatment or when other findings strongly support ABPA. Your clinician must interpret each result in the context of your treatment and the rest of the diagnostic criteria.

Questions For You

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Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my total IgE level meet the threshold of 500 IU/mL required by the 2024 ISHAM criteria?
  2. 2.Was my Aspergillus-specific IgE test positive (above 0.35 kUA/L), and does that confirm sensitization?
  3. 3.Does my CT scan show 'High-Attenuation Mucus' (HAM), and what does that mean for my diagnosis?
  4. 4.Based on the 2024 criteria, do I have at least two of the three 'supportive' markers (specific IgG, high eosinophils, or suggestive imaging)?
  5. 5.Are my current eosinophil levels being affected by any steroids or biologics I am already taking?

References

References (17)
  1. 1

    Revised ISHAM-ABPA working group clinical practice guidelines for diagnosing, classifying and treating allergic bronchopulmonary aspergillosis/mycoses.

    Agarwal R, Sehgal IS, Muthu V, et al.

    The European respiratory journal 2024; (63(4)) doi:10.1183/13993003.00061-2024.

    PMID: 38423624
  2. 2

    Allergic bronchopulmonary aspergillosis and Aspergillus-related airway diseases in bronchiectasis: a narrative review.

    Agarwal R, Chotirmall SH, Chalmers JD

    Journal of thoracic disease 2025; (17(12)):11501-11519 doi:10.21037/jtd-2025-1548.

    PMID: 41522133
  3. 3

    A decision tree analysis to evaluate the optimal approach to screen allergic bronchopulmonary aspergillosis in asthmatic patients.

    Agarwal R, Sehgal IS, Saxena P, et al.

    The Journal of asthma : official journal of the Association for the Care of Asthma 2025; (62(5)):761-766 doi:10.1080/02770903.2024.2439994.

    PMID: 39641611
  4. 4

    Allergic bronchopulmonary aspergillosis misdiagnosed as recurrent pneumonia.

    Jiang N, Xiang L

    Asia Pacific allergy 2020; (10(3)):e27 doi:10.5415/apallergy.2020.10.e27.

    PMID: 32789112
  5. 5

    Omalizumab in allergic bronchopulmonary aspergillosis in patients with cystic fibrosis.

    Ashkenazi M, Sity S, Sarouk I, et al.

    Journal of asthma and allergy 2018; (11()):101-107 doi:10.2147/JAA.S156049.

    PMID: 29950869
  6. 6

    Utility of IgE (total and Aspergillus fumigatus specific) in monitoring for response and exacerbations in allergic bronchopulmonary aspergillosis.

    Agarwal R, Aggarwal AN, Sehgal IS, et al.

    Mycoses 2016; (59(1)):1-6 doi:10.1111/myc.12423.

    PMID: 26575791
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    Coexisting atopic conditions influence the likelihood of allergic bronchopulmonary aspergillosis in asthma.

    Tay TR, Bosco J, Gillman A, et al.

    Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology 2016; (117(1)):29-32.e1.

    PMID: 27234940
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    Mepolizumab as Possible Treatment for Allergic Bronchopulmonary Aspergillosis: A Review of Eight Cases.

    Tolebeyan A, Mohammadi O, Vaezi Z, Amini A

    Cureus 2020; (12(8)):e9684 doi:10.7759/cureus.9684.

    PMID: 32923277
  9. 9

    [Allergic bronchopulmonary aspergillosis-essential knowledge for radiology].

    Salhöfer L, Welsner M, Lehmann H, et al.

    Radiologie (Heidelberg, Germany) 2026; (66(3)):169-176 doi:10.1007/s00117-026-01567-w.

    PMID: 41632270
  10. 10

    High attenuation mucus in bronchi with allergic bronchopulmonary mycosis.

    Hattori S, Oguma T, Ishiguro T, et al.

    Mycoses 2024; (67(2)):e13705 doi:10.1111/myc.13705.

    PMID: 38369597
  11. 11

    High-Attenuation Mucus Impaction in Patients With Allergic Bronchopulmonary Aspergillosis: Objective Criteria on High-Resolution Computed Tomography and Correlation With Serologic Parameters.

    Phuyal S, Garg MK, Agarwal R, et al.

    Current problems in diagnostic radiology 2016; (45(3)):168-73.

    PMID: 26323654
  12. 12

    CT evaluation of hyperattenuating mucus to diagnose allergic bronchopulmonary aspergillosis in the special condition of cystic fibrosis.

    Refait J, Macey J, Bui S, et al.

    Journal of cystic fibrosis : official journal of the European Cystic Fibrosis Society 2019; (18(4)):e31-e36 doi:10.1016/j.jcf.2019.02.002.

    PMID: 30765182
  13. 13

    Biomarkers for the Diagnosis of Allergic Bronchopulmonary Aspergillosis in Cystic Fibrosis: A Systematic Review and Meta-Analysis.

    Li BCM, Huh SM, Prieto MD, et al.

    The journal of allergy and clinical immunology. In practice 2021; (9(5)):1909-1930.e4 doi:10.1016/j.jaip.2020.12.064.

    PMID: 33454395
  14. 14

    New insights into the treatment of asthma complicated by allergic bronchopulmonary aspergillosis.

    Agarwal R, Muthu V, Sehgal IS

    Expert review of respiratory medicine 2025; (19(9)):967-979 doi:10.1080/17476348.2025.2517302.

    PMID: 40474578
  15. 15

    [Allergic bronchopullmonary aspergillosis (ABPA) - an Update].

    Joest M, Klein J, Kütting D, Skowasch D

    Pneumologie (Stuttgart, Germany) 2024; (78(3)):204-214 doi:10.1055/a-1854-3006.

    PMID: 38417459
  16. 16

    Clinical Manifestation and Treatment of Allergic Bronchopulmonary Aspergillosis.

    Agarwal R, Muthu V, Sehgal IS

    Seminars in respiratory and critical care medicine 2024; (45(1)):114-127 doi:10.1055/s-0043-1776912.

    PMID: 38154470
  17. 17

    Clinical Analysis of 77 Patients with Allergic Bronchopulmonary Aspergillosis in Peking Union Medical College Hospital.

    Zhang M, Gao J

    Zhongguo yi xue ke xue yuan xue bao. Acta Academiae Medicinae Sinicae 2017; (39(3)):352-357 doi:10.3881/j.issn.1000-503X.2017.03.009.

    PMID: 28695805

This page explains ABPA testing and the 2024 ISHAM criteria for informational purposes only and does not constitute medical advice. Ask your clinician to interpret your results in the context of your medications and health history.