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Alpha-Lactalbumin-Specific IgA Antibody (RAST)

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

A blood test that measures IgA antibodies directed against alpha-lactalbumin, a protein found in milk.

Quick summary

["This test helps evaluate an immune response to the milk protein alpha-lactalbumin."]

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

Key facts at a glance

LOINC
102877-8
Short code
A-Lactalb IgA RAST
Synonyms
A-Lactalb IgA RAST
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
Method
rast
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 RAST blood test measures IgA antibodies directed against alpha-lactalbumin, a milk protein. The result can provide information about your immune response to this protein.

Why might I need this test?

A clinician may order this test when symptoms suggest a reaction or sensitivity to milk or milk products. It may be used alongside your medical history, other allergy testing, and a food-elimination and reintroduction plan.

How is the test performed?

A blood sample is collected and analyzed in a laboratory for antibodies to alpha-lactalbumin. The laboratory reports the antibody level or whether antibodies were detected.

How do I prepare for the test?

No special preparation is usually required for this blood test unless your healthcare professional gives different instructions. Tell the clinician about your symptoms, milk exposure, medications, supplements, and any diagnosed food 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

Alpha-Lactalbumin IgA (RAST)

Frequently asked questions

What does alpha-lactalbumin IgA mean?
It is an immune-system antibody directed against alpha-lactalbumin, a protein found in milk. A positive result is not automatically the same as having a milk allergy.
Is this the same as a milk allergy test?
It tests the response to one specific milk protein, so it does not evaluate every milk protein or other possible cause of symptoms. Your clinician may combine it with other tests and your history.
Do I need to avoid milk before the test?
Do not deliberately avoid milk unless your clinician instructs you to do so. The result can be easier to interpret when the testing reflects your usual diet and symptoms.
  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