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Penicillium betae–Specific IgG Radioallergosorbent Test (RAST), Qualitative (Deprecated)

Published: August 9, 2026Updated: August 17, 2026

A legacy blood test that qualitatively detects IgG antibodies to the mold Penicillium betae. It may indicate exposure or sensitization but does not by itself diagnose allergy.

Quick summary

["A positive result suggests an immune response to P. betae, but this deprecated IgG test alone does not confirm a clinical allergy."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
33303-9
Short code
Deprecated P betae IgG RAST Ql
Synonyms
Deprecated P betae IgG 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 is a radioallergosorbent test, or RAST, that looks for IgG antibodies directed against the mold Penicillium betae in a blood sample. It reports the result qualitatively, usually as positive or negative.

Why might I need this test?

It may have been used to assess whether a person had developed an immune response to this mold. Results must be interpreted with symptoms, exposure history, and other allergy testing because a positive IgG result does not necessarily mean that mold is causing allergy symptoms.

How is the test performed?

A blood sample is tested in the laboratory using RAST methodology, which detects allergen-specific antibodies. Because this is a qualitative test, the final report indicates whether detectable antibodies were found.

How do I prepare for the test?

No special preparation is generally required for a routine blood draw. Follow any instructions provided by the ordering clinician and tell the laboratory about medicines, recent infections, and known allergies.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

P. betae IgG RAST

Frequently asked questions

Does a positive result mean I am allergic to P. betae?
Not necessarily. The test detects IgG antibodies, which can indicate exposure or sensitization, while clinical allergy is usually associated with IgE-mediated symptoms. Your clinician should interpret the result alongside your history and examination.
Why is the test described as deprecated?
Deprecated means it is a legacy test that is no longer routinely recommended or may no longer be available. A clinician may suggest newer, more specific allergy testing based on your symptoms.
Do I need to stop allergy medicines before this test?
Do not stop medicines without instructions from your clinician. Because this test detects IgG rather than IgE, common antihistamines generally have less direct effect, but the laboratory's preparation instructions should take priority.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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