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Alfalfa-Specific IgG Antibodies, Qualitative — Radioallergosorbent Test (RAST)

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

A blood test that detects antibodies directed against alfalfa. Results may reflect prior exposure but do not by themselves confirm a clinical allergy.

Quick summary

["This test measures the immune response to alfalfa but cannot determine allergy on its own."]

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

Key facts at a glance

LOINC
21061-7
Short code
Deprecated Alfalfa IgG RAST Ql
Synonyms
Deprecated Alfalfa 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 qualitative blood test detects alfalfa-specific IgG antibodies using radioallergosorbent testing, or RAST. IgG antibodies commonly develop after exposure to an allergen and are different from the IgE antibodies more closely associated with immediate allergic reactions.

Why might I need this test?

A clinician may order this test to evaluate immune sensitization after exposure to alfalfa or as part of an allergy evaluation. It may be considered alongside your symptoms, medical history, and other allergy tests.

How is the test performed?

A blood sample is collected and analyzed in a laboratory for antibodies that recognize alfalfa. Because the result is qualitative, it generally reports whether detectable antibodies are present rather than providing a measured concentration.

How do I prepare for the test?

No special preparation is usually required, and fasting is generally unnecessary unless your healthcare professional gives different instructions. Tell the clinician about allergic symptoms, recent alfalfa exposure, relevant medicines, and any other allergy testing you have had.

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

Alfalfa-specific IgG

Frequently asked questions

Does a positive result mean I am allergic to alfalfa?
Not necessarily. Alfalfa-specific IgG can occur after exposure without causing symptoms, so the result must be interpreted with your history and other allergy evidence.
Is this the same as an alfalfa-specific IgE test?
No. This test detects IgG antibodies, while IgE-specific testing evaluates a different type of immune response that is more closely associated with immediate allergy.
Why was this test ordered if I have allergy symptoms?
It may be one part of an allergy evaluation. Your clinician may also consider symptom timing, skin-prick testing, or other tests when determining whether alfalfa is responsible.
  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