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HIV Antibody and Antigen P24 Protein Test (Serum/Plasma)

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

This test detects antibodies and the p24 protein, key markers of HIV infection, in your blood or plasma. It helps determine whether you have been exposed to HIV.

Quick summary

["Identifies HIV infection through antibody and p24 protein detection in blood or plasma."]

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

Key facts at a glance

LOINC
5222-5
Short code
HIV1 Ag SerPl Ql IA
Synonyms
HIV1 Ag SerPl Ql IA
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

How the Test Works

The test uses an immunoassay method to measure two components: HIV antibodies (which develop after initial infection) and the p24 protein (found in early stages). If both are present, it confirms HIV infection. The sample is drawn from your vein and processed to detect these markers.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood, which usually causes minimal discomfort. If you’re nervous, let your healthcare provider know—they can offer options to ease anxiety.

When You Might Need This Test

Your doctor may recommend this test if you have risk factors for HIV (e.g., unprotected sex, shared needles, or recent travel to areas with higher infection rates), or if you’re experiencing symptoms like fatigue, fever, or unexplained weight loss. It’s also part of routine screening for sexually active individuals.

What the Results Mean

A positive result means you likely have HIV and should seek immediate medical care for treatment and support. A negative result means you are not currently infected, but you may still need follow-up testing if you have risk factors. Results are not definitive without confirmation testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

HIV Screen/Confirm

Frequently asked questions

Why is this test important?
Early detection of HIV allows for prompt treatment, which can slow disease progression and improve long-term health outcomes. This test helps monitor infection status, guide treatment decisions, and reduce transmission risk to others.
How soon after exposure can I get tested?
HIV antibodies take about 2–12 weeks to develop after exposure, but the p24 protein may appear earlier. If you suspect exposure, ask your doctor about testing at specific time points or window periods.
Can I get false positives or false negatives?
False positives are rare but possible, especially in early infection. False negatives can occur if tested too soon after exposure. Follow-up testing may be needed if initial results are unclear.
  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