Test library
HIV 4th Generation Test
The HIV 4th generation test detects both HIV antibodies and the p24 antigen in a blood sample. Combining the two markers narrows the window period and allows earlier detection after exposure.
Order HIV 4th Generation Antigen/Antibody Test
Order online and visit a local collection site, or choose an at-home kit where available. No referral and no insurance required.
Order HIV 4th Generation Antigen/Antibody Test- Typical turnaround
- 1-3 business days
- Starting price
- From $49
- Results
- Confidential, online
Quick answer
The HIV 4th Generation Antigen/Antibody Test, often called the DUO test, looks for both HIV antibodies and the p24 antigen in a blood sample. Earlier generation tests detected only antibodies, which take weeks to develop. Adding the antigen marker allows the test to detect infection sooner after exposure, though a window period still applies.
What this test measures
When HIV enters the body, the p24 antigen appears in the blood before antibodies form. A fourth generation test measures both, so it can detect infection earlier than antibody-only tests. This combined approach has become the standard initial screen for HIV in many laboratories.
The sample is blood drawn from a vein. If the combined screen is reactive, a follow-up test is performed to confirm the result and to distinguish HIV-1 from HIV-2 where relevant. Screening tests are designed to be sensitive, so a reactive screen is not final until confirmatory testing is complete.
No test can detect infection immediately after exposure, because the virus and the immune response both take time to become measurable. A healthcare provider can advise on when to test and whether repeat testing is appropriate. Results are confidential and should be discussed with a qualified provider.
- HIV-1/2 antigen and antibody combination
- HIV p24 antigen
- HIV-1 antibodies
- HIV-2 antibodies
- HIV-1/2 antibody differentiation (reflex)
- HIV-1 RNA (reflex when indicated)
Why people order this test
- Screen for HIV after a possible exposure
- Use a test that shortens the window period
- Routine sexual health screening
- Follow up on a reactive result from another test
- Check status before a new relationship with a provider
- Meet testing requirements for certain programs
How to prepare
No fasting is required for this blood test. A sample is drawn from a vein, usually at the arm. Because a window period applies, ask the laboratory or a healthcare provider about the best time to test after a possible exposure.
Understanding your results
Results are typically available within one to three business days. A non-reactive result means no markers were detected at the time of collection. A reactive screen requires confirmatory testing before any result is treated as final.
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Frequently Asked Questions
How is the 4th generation HIV test different?
It detects both HIV antibodies and the p24 antigen. Because the antigen appears earlier, the test can find infection sooner than antibody-only tests.
How soon can this test detect HIV?
It can detect infection earlier than older antibody tests, but a window period still applies. A provider can advise on the best timing for testing and any repeat.
What does a reactive result mean?
A reactive screening result is not a final diagnosis. It is followed by confirmatory testing to determine whether HIV is actually present.
Is the result confidential?
Yes. HIV testing is handled with confidentiality, and results are shared with the person and their provider as part of appropriate care.
Do I need to fast?
No fasting is required for this blood test.
Ready to get tested?
Order online and visit a collection site near you, or choose a mail-in kit. No referral and no insurance required.
Reviewed by the LabOrdering Editorial Team
Every page on this site is reviewed for clarity, sourcing, and accuracy. We update our library as testing options, collection networks, and accreditation standards change.