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Serum or Plasma Immunoassay for Immunoglobulin M (IgM) Antibody to Hepatitis A Virus

Published: August 9, 2026Updated: August 16, 2026

This test measures the presence of IgM antibodies against the hepatitis A virus in your blood. IgM antibodies appear early in an infection and can help identify recent hepatitis A exposure.

Quick summary

["Detects recent hepatitis A virus infection with IgM antibodies, useful for diagnosing acute illness."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
101123-8
Short code
blaIMI
Synonyms
blaIMI Islt/Spm Ql
Category
chemistry
Sample
serum
Container
Sterile transport container or appropriate bacterial culture transport medium (e.g., Amies or Stuart transport medium); for serum, use serum separator tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
0–999 years
Method
molgen
CPT
87798 (unlisted molecular detection); or 87150 (carbapenemase detection)
SNOMED
122450005 | Carbapenemase-producing organism | or 122451009 | Carbapenem resistance gene detected |
Specimen volume
1-2 mL serum; for bacterial culture: isolated colony on appropriate media or primary specimen in transport medium
Stability
Serum: stable for 24 hours at 2-8°C; bacterial isolates: stable for up to 7 days at 2-8°C on appropriate media; DNA extracts stable at -20°C to -80°C for long-term storage
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–72 hours
Order
routine

What Does This Test Measure?

IgM antibodies are a type of immune protein your body produces in response to a recent infection. In this test, we look for IgM antibodies specifically against the hepatitis A virus (HAV). These antibodies typically appear within 2 to 6 weeks after exposure to the virus and can stay in your system for several months. This test helps doctors determine if you’ve recently been infected with hepatitis A, which can cause liver inflammation and illness.

Why Might You Need This Test?

Your healthcare provider may recommend this test if you have symptoms of hepatitis A, such as fatigue, nausea, abdominal pain, jaundice (yellowing of the skin or eyes), or dark urine. It may also be used in people who have recently traveled to areas with higher rates of hepatitis A or those who have had close contact with someone who has the virus.

What to Expect During the Test

A small blood sample will be taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause much discomfort. The blood is then sent to a lab for testing. Results are typically available within a few days.

What Are the Possible Results?

If the test shows a positive result for IgM antibodies against hepatitis A, it suggests you’ve recently been infected. A negative result means you likely haven’t had recent exposure to the virus. It’s important to note that IgM antibodies can sometimes remain in your system for months after recovery, so this test alone isn’t definitive for past infection without additional testing.

Reference range

Negative (blaIMI gene not detected). Reference range applies to qualitative detection of the blaIMI carbapenem resistance gene in bacterial isolates or specimens.N/A

Specimen: serum

No special patient preparation required. Specimen should be collected prior to initiation of antibiotic therapy when possible for optimal recovery of organism. Follow standard infection control precautions during collection.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgM Anti-HAV

Frequently asked questions

This test plays a critical role in diagnosing acute hepatitis A, which can be serious but is usually treatable. Early detection allows for prompt medical care, which can ease symptoms and prevent complications. It’s also important for public health tracking, especially in outbreaks or high-risk populations.
How soon after exposure can this test detect hepatitis A infection?
IgM antibodies against hepatitis A can be detected as early as 2 weeks after exposure, but symptoms may not appear until 2 to 6 weeks later. The test is most accurate when performed within this window, though it may still be useful if symptoms are present.
No, this test specifically measures IgM antibodies, which are associated with recent infection. To confirm past infection, your doctor may order an IgG antibody test or a combined IgM/IgG test, which can detect antibodies from both recent and past infections.
What should I do if my test result is positive for IgM antibodies against hepatitis A?
If your test result is positive, your healthcare provider will likely recommend follow-up testing to confirm the diagnosis and monitor your liver function. They may also provide guidance on managing symptoms, staying hydrated, and avoiding alcohol. In some cases, they may prescribe medications to support liver health or reduce 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 16, 2026. · Read our editorial policy