Aspergillus fumigatus IgG4 Antibodies — Radioallergosorbent Test (RAST), Qualitative (Deprecated)
A qualitative blood test that detects Aspergillus fumigatus–specific IgG4 antibodies to help evaluate suspected Aspergillus-related lung disease.
["A positive result shows detectable Aspergillus fumigatus–specific IgG4 antibodies but does not by itself diagnose allergy or infection."]
Key facts at a glance
- LOINC
- 26406-9
- Short code
- Deprecated A fumigatus IgG4 RAST Ql
- Synonyms
- Deprecated A fumigatus IgG4 RAST Ql
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84484
- SNOMED
- 302774002
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test looks for IgG4 antibodies directed against Aspergillus fumigatus, a mold commonly found in the environment. The result is qualitative, meaning it is generally reported as positive or negative. This test designation is marked as deprecated, so a clinician may need to discuss a current alternative.
Why might I need this test?
A clinician may order it when evaluating chronic cough, wheezing, recurrent lung infections, bronchiectasis, or other suspected Aspergillus-related lung conditions. Results are interpreted with symptoms, imaging, lung-function tests, and other laboratory findings.
How is the test performed?
A blood sample is collected and tested in the laboratory using a RAST-type allergen-antibody method. The laboratory reports whether Aspergillus fumigatus–specific IgG4 antibodies were detected.
How do I prepare for the test?
Fasting is usually not required for this blood test, but follow the laboratory's instructions. Tell your clinician about immune or lung conditions, medications, recent Aspergillus exposure, and any prior allergy testing; do not stop prescribed medicines unless your clinician advises you to do so.
Reference range
Adult: 10-40 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A positive result means that Aspergillus fumigatus–specific IgG4 antibodies are detectable, which can reflect prior exposure or an immune response. It does not by itself prove active fungal infection, allergy, or allergic bronchopulmonary aspergillosis. A negative result does not completely exclude these conditions, so results must be interpreted alongside the clinical evaluation.
Short name
Aspergillus fumigatus IgG4 (RAST)
Frequently asked questions
What does a positive result mean?
Does this test diagnose allergic bronchopulmonary aspergillosis?
Is fasting or medication adjustment required?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy