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Immunoglobulin G (IgG)-to-Aspartate Aminotransferase (AST) Ratio, Qualitative (Deprecated Test Code)

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

A laboratory comparison of blood IgG and AST that may help evaluate liver inflammation and fibrosis in some liver diseases.

Quick summary

["This test combines two blood markers to provide additional information about liver injury and immune-mediated liver disease."]

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

Key facts at a glance

LOINC
21430-4
Short code
Deprecated Onion IgG RAST Ql
Synonyms
Deprecated Onion 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 test compares immunoglobulin G (IgG), an antibody, with aspartate aminotransferase (AST), a liver enzyme found in several tissues. The ratio may provide additional information in the evaluation of chronic liver disease.

Why might I need this test?

A clinician may order it when liver tests are abnormal or when a condition affecting the liver is being monitored. The result is generally considered alongside other laboratory findings, imaging, and your medical history.

How is the test performed?

A laboratory sample is used to measure AST and IgG. The laboratory then applies the specified ratio or qualitative interpretation, depending on the test method.

How do I prepare for the test?

Fasting is usually not required, but preparation can vary by laboratory and clinical situation. Follow the instructions provided by your clinician or testing laboratory, and tell them about recent illness, liver conditions, medications, and alcohol use.

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

IgG-to-AST ratio

Frequently asked questions

What does the IgG-to-AST ratio measure?
It compares the amount of IgG with the amount of AST in the tested sample. The information may help assess liver injury and immune activity together.
Does this test require fasting?
Fasting is commonly unnecessary, although your clinician or laboratory may provide specific instructions. Confirm the preparation requirements before the test.
Can an abnormal result diagnose liver fibrosis?
No. The result may contribute to a clinician's assessment, but fibrosis usually requires additional evidence, such as other laboratory tests, imaging, and sometimes a liver biopsy.
  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