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HIV p24 Antigen Quantitative Serum/Plasma

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

This test measures the amount of p24 protein in your blood or serum/plasma. It helps detect HIV infection by identifying early viral presence.

Quick summary

["Detects HIV early with a blood test for p24 antigen."]

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

Key facts at a glance

LOINC
53601-1
Short code
HIV1 p24 Ag SerPl IA-aCnc
Synonyms
HIV1 p24 Ag SerPl IA-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
CPT
86701
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 the Purpose of This Test?

This test is used primarily to screen for HIV infection. It detects the p24 protein, a marker of the HIV virus, which appears in your blood shortly after infection. Early detection is crucial for managing the disease and starting appropriate treatment if needed.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is then processed to measure the concentration of p24 antigen in your serum or plasma.

What Does a Positive Result Mean?

A positive result indicates the presence of HIV p24 antigen, suggesting active HIV infection. However, false positives can occur, so further testing (like HIV antibody tests) is often needed for confirmation.

What Does a Negative Result Mean?

A negative result means the test did not detect p24 antigen at the time of testing. This does not guarantee you are not infected—HIV can be present without detectable p24 antigen early in infection. Follow-up testing may be recommended.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test plays a key role in early HIV detection. While HIV antibody tests are more commonly used for screening, p24 antigen testing can identify infection sooner, especially in the first few months after exposure. Early diagnosis allows for timely medical intervention, which can improve long-term health outcomes.

Short name

HIV p24 Antigen

Frequently asked questions

Why might I need this test?
You may need this test if you have recently been exposed to HIV, have symptoms of infection, or are part of a high-risk group for HIV. Your healthcare provider may also recommend it as part of routine testing or follow-up.
What are the possible side effects of this blood test?
The most common side effect is a mild bruise, redness, or slight pain at the injection site. Rarely, you might experience a slight swelling or discomfort. Most side effects resolve within a few days.
Can I drink alcohol before this test?
It is generally recommended to avoid alcohol for 24 hours before the test to ensure accurate results. Alcohol can sometimes affect blood test results, so follow your healthcare provider’s specific instructions.
  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