HIV/AIDS Blood Test Types: Names, How They Work, and Accuracy

• The main blood test names for HIV/AIDS include the ELISA (EIA) screening test, Western blot confirmatory test, fourth-generation antigen/antibody tests, and nucleic acid tests (NAT/PCR).
• Fourth-generation antigen/antibody combination tests are the recommended first-line screening method in the United States because they detect HIV earlier than older antibody-only tests.
• The Western blot is no longer the recommended confirmatory test; the CDC's current algorithm uses an HIV-1/HIV-2 differentiation immunoassay for confirmation.
• HIV test accuracy exceeds 99% when performed after the appropriate window period, which ranges from 10 days for NAT to 90 days for some antibody tests.
• At-home HIV test kits like OraQuick provide rapid results using oral fluid, while laboratory-based tests using venous blood offer the highest sensitivity and earliest detection.

This guide was developed using official resources from the Centers for Disease Control and Prevention (CDC), the U.S. Food and Drug Administration (FDA), the Clinical Laboratory Improvement Amendments (CLIA) program, the World Health Organization (WHO), and HIV.gov. We reviewed the current CDC HIV diagnostic testing algorithm, FDA-approved test listings, and peer-reviewed literature on HIV test performance characteristics. All test names, accuracy data, window periods, and guideline recommendations reflect the most current published evidence as of April 2026. This content was reviewed by professionals specializing in infectious disease, clinical pathology, and HIV medicine.

Understanding the names and types of HIV blood tests can feel like navigating an alphabet soup of medical terminology. This guide breaks down every major test name, explains what each one does, and helps you understand which tests are used when.

The Current CDC HIV Testing Algorithm

The CDC updated its recommended HIV testing algorithm to reflect advances in testing technology. Understanding this algorithm provides the framework for all the test names discussed below.

The current recommended sequence is:

1. Initial screening: A fourth-generation antigen/antibody combination test (detects both HIV antibodies and the p24 antigen)
2. If positive, confirmatory differentiation: An HIV-1/HIV-2 antibody differentiation immunoassay (determines whether the infection is HIV-1 or HIV-2)
3. If indeterminate or discrepant: HIV-1 nucleic acid test (NAT) to resolve the result

This algorithm replaced the older sequence of ELISA followed by Western blot confirmation, though some laboratories still use variations of both approaches.

1. ELISA (Enzyme-Linked Immunosorbent Assay) / EIA (Enzyme Immunoassay)

Test names you may see: ELISA, EIA, HIV-1/HIV-2 EIA, HIV antibody screening test

The ELISA (also called EIA) was historically the standard first-line screening test for HIV. It detects antibodies to HIV-1 and HIV-2 in the blood.

How it works:

• A blood sample is added to a plate or well coated with HIV proteins (antigens).
• If HIV antibodies are present in the blood, they bind to these antigens.
• An enzyme-linked detection antibody is added that produces a color change if the HIV antibodies are present.
• The intensity of the color change is measured to determine whether the result is positive or negative.

Accuracy: Third-generation ELISA tests have sensitivity and specificity exceeding 99% after the window period.

Window period: 23 to 90 days after infection.

Current status: While the ELISA methodology is still used in many laboratory tests, standalone third-generation ELISA tests are no longer the recommended first-line screening method in the United States. They have been largely replaced by fourth-generation antigen/antibody combination tests.

2. Fourth-Generation Antigen/Antibody Combination Tests

Test names you may see:

• Abbott ARCHITECT HIV Ag/Ab Combo
• Bio-Rad GS HIV Combo Ag/Ab EIA
• Siemens ADVIA Centaur HIV Ag/Ab Combo
• Roche Elecsys HIV Duo
• Fourth-generation HIV test
• HIV combo test
• HIV Ag/Ab test

Fourth-generation tests represent the current gold standard for initial HIV screening. They simultaneously detect HIV-1 and HIV-2 antibodies AND the HIV-1 p24 antigen.

How they work:

• The test uses a combination approach that captures both the p24 antigen (a protein from the HIV virus itself) and antibodies to both HIV-1 and HIV-2.
• The p24 antigen appears in the blood within days of infection, before the immune system has produced detectable levels of antibodies.
• By detecting the p24 antigen, fourth-generation tests can identify HIV infection approximately one to three weeks earlier than antibody-only (third-generation) tests.

Accuracy: Sensitivity and specificity exceeding 99.5% after the window period. These are among the most accurate screening tests available for any infectious disease.

Window period: 18 to 45 days after infection.

Why they are preferred: The CDC recommends fourth-generation tests as the initial screening test because they significantly reduce the window period compared to antibody-only tests, allowing for earlier diagnosis and earlier initiation of treatment.

3. Western Blot

Test names you may see: HIV-1 Western blot, HIV Western blot assay, immunoblot

The Western blot was historically the standard confirmatory test used to verify a positive ELISA result. However, its role has changed significantly.

How it works:

• HIV proteins are separated by size using gel electrophoresis.
• The separated proteins are transferred to a membrane.
• The patient's blood sample is applied to the membrane.
• If HIV antibodies are present, they bind to specific HIV proteins on the membrane.
• The pattern of binding is visualized and interpreted according to established criteria.
• A positive result requires detection of specific bands corresponding to HIV proteins (such as gp120/gp160, gp41, and p24).

Accuracy: When used as a confirmatory test after a positive screening test, the Western blot has specificity approaching 100%. However, its sensitivity during early infection is lower than newer methods, which is one reason it has been replaced in the current algorithm.

Current status: The Western blot is no longer recommended as the primary confirmatory test in the CDC's current HIV diagnostic algorithm. It has been replaced by the HIV-1/HIV-2 differentiation immunoassay. However, the Western blot is still used in some settings and some laboratories, and some providers may still refer to it.

4. HIV-1/HIV-2 Differentiation Immunoassay

Test names you may see:

• Geenius HIV 1/2 Supplemental Assay (Bio-Rad)
• Multispot HIV-1/HIV-2 Rapid Test
• HIV-1/HIV-2 differentiation assay
• HIV supplemental test

This is the currently recommended confirmatory test in the CDC algorithm, replacing the Western blot.

How it works:

• The test uses immobilized HIV-1 and HIV-2 specific proteins on a test strip or membrane.
• The patient's blood sample is applied, and if HIV antibodies are present, they bind to the specific proteins.
• The test can differentiate between HIV-1 (the most common type worldwide) and HIV-2 (less common, primarily found in West Africa).
• Results are typically available within 30 minutes.

Why it replaced the Western blot: The differentiation immunoassay provides faster results, can distinguish between HIV-1 and HIV-2 (important for treatment decisions), and has better performance characteristics for confirming recent infections.

5. Nucleic Acid Tests (NAT) / PCR Tests

Test names you may see:

• HIV-1 RNA qualitative test
• HIV-1 NAT
• HIV PCR test
• HIV viral load test (quantitative)
• Aptima HIV-1 RNA qualitative assay
• Cobas HIV-1/HIV-2 qualitative test (Roche)

NAT directly detects the genetic material (RNA) of the HIV virus, rather than the body's immune response to it.

How they work:

• The test uses polymerase chain reaction (PCR) technology or similar nucleic acid amplification methods.
• These techniques amplify tiny amounts of HIV RNA in the blood sample to detectable levels.
• Qualitative NAT determines whether HIV RNA is present (positive or negative result).
• Quantitative NAT (viral load test) measures the amount of HIV RNA in the blood, reported as copies per milliliter.

When NAT is used:

• Resolving indeterminate results: When the screening test is positive but the confirmatory test is negative or indeterminate.
• Detecting acute HIV infection: When symptoms suggest very recent HIV infection but antibody tests are still negative.
• Monitoring treatment: Quantitative NAT (viral load) is used to monitor the effectiveness of antiretroviral therapy in people diagnosed with HIV.
• Blood supply screening: NAT is used to screen all donated blood in the United States.

Accuracy: Sensitivity approaching 100% after the window period. NAT can detect as few as 20-50 copies of HIV RNA per milliliter of blood, depending on the specific assay.

Window period: 10 to 33 days after infection, the shortest of any HIV test type.

6. Rapid HIV Tests

Test names you may see:

• OraQuick Advance Rapid HIV-1/2 Antibody Test
• INSTI HIV-1/HIV-2 Antibody Test
• Clearview HIV-1/2 Stat-Pak
• Uni-Gold Recombigen HIV Test
• Rapid HIV test

Rapid HIV tests are designed to provide results quickly, typically within 20 minutes, without the need for laboratory processing equipment.

How they work:

• Most rapid tests use lateral flow or flow-through technology, similar to a home pregnancy test.
• A sample (blood from a finger prick, oral fluid, or plasma) is applied to the test device.
• The sample flows along a test strip containing HIV antigens.
• If HIV antibodies are present, they bind to the antigens and produce a visible line or color change.

Types:

• Antibody-only rapid tests: Detect HIV antibodies. Window period of 23 to 90 days.
• Rapid antigen/antibody tests: Detect both HIV antibodies and p24 antigen. Window period of 18 to 45 days.

Accuracy: Sensitivity and specificity of approximately 99% after the window period, slightly lower than laboratory-based tests.

7. At-Home HIV Test Kits

Test names you may see:

• OraQuick In-Home HIV Test
• Home Access HIV-1 Test System
• Home HIV test
• Self-test HIV kit

FDA-approved at-home HIV tests fall into two categories:

Self-testing (result at home):

• The OraQuick In-Home HIV Test uses an oral fluid swab and provides results in 20 minutes. No blood draw required.
• Sensitivity: approximately 92% (meaning about 1 in 12 people with HIV may receive a false negative)
• Specificity: approximately 99.9%

Home collection (sample sent to lab):

• The Home Access HIV-1 Test System involves pricking your finger, collecting blood on a card, and mailing it to a laboratory.
• Results are provided by phone using an anonymous code.
• Laboratory accuracy (sensitivity and specificity exceeding 99%).

Important note: Because the OraQuick in-home test uses oral fluid and is a rapid antibody test, it has a longer effective window period (up to 3 months) and slightly lower sensitivity than laboratory-based tests. A positive result from any at-home test must be confirmed with follow-up laboratory testing.

What to Expect When Getting Tested

1. Pre-test counseling (brief): A healthcare provider explains the test, answers questions, and discusses risk factors. In many settings, this has been streamlined to a brief conversation or written information.

2. Sample collection: Depending on the test type, this may involve a blood draw from a vein, a finger prick, or an oral fluid swab.

3. Waiting for results: Rapid tests provide results in about 20 minutes. Laboratory-based tests typically take 1 to 5 business days.

4. Post-test counseling: A healthcare provider explains the results, discusses next steps, and provides referrals if needed.

Understanding Your Results

Negative result:

• HIV was not detected in your sample.
• If you were tested within the window period, you may need repeat testing to confirm the result.
• A negative result means only that HIV was not detected at the time of testing, not that you are immune to future infection.

Positive result:

• HIV was detected and requires confirmatory testing.
• A positive screening test is preliminary until confirmed by additional testing.
• If confirmed, early treatment with antiretroviral therapy (ART) can keep you healthy and reduce your viral load to undetectable levels, effectively eliminating the risk of transmission (Undetectable = Untransmittable, or U=U).

Indeterminate result:

• The test did not clearly indicate positive or negative.
• This can occur during early infection when antibody levels are still developing, or due to cross-reactivity with other conditions.
• Follow-up testing with NAT or repeat testing at a later date is recommended.

Several factors can influence the reliability of HIV test results:

Timing of the test relative to exposure: Testing too early, during the window period, is the most common cause of false negative results.

Type of sample collected: Venous blood generally provides the most accurate results, followed by finger prick blood, with oral fluid being the least sensitive sample type.

Test generation and type: Fourth-generation tests are more sensitive than third-generation tests during early infection. NAT provides the earliest detection.

Biological factors: Rare conditions such as autoimmune disorders, recent vaccinations, or other infections can occasionally cause false positive results on screening tests, which is why confirmatory testing is essential.

Proper sample handling: Laboratory conditions, sample storage, and transport can affect results, particularly for tests that require specialized processing.

Understanding the names and types of HIV/AIDS blood tests empowers you to have informed conversations with your healthcare provider and make confident decisions about your sexual health. The key test names to know include:

• Fourth-generation antigen/antibody tests (Abbott ARCHITECT, Bio-Rad GS HIV Combo) are the current recommended first-line screening tests, detecting HIV earlier than any antibody-only test.
• HIV-1/HIV-2 differentiation immunoassays (Geenius) have replaced the Western blot as the recommended confirmatory test.
• Nucleic acid tests (NAT/PCR) provide the earliest detection and are used to resolve unclear results.
• Rapid tests and at-home tests offer convenience and accessibility, though with slightly lower sensitivity than laboratory-based options.

The most important action you can take is to get tested. Regardless of which specific test name appears on the order form, any HIV test performed after the appropriate window period provides reliable results. If you have never been tested, or if you have had potential exposure since your last test, contact a healthcare provider, community clinic, or use an FDA-approved home test kit. Knowing your HIV status is one of the most powerful steps you can take for your health and the health of your community.

What is the name of the blood test for HIV/AIDS?

There is no single test name. The most commonly used blood test for HIV screening today is called a fourth-generation antigen/antibody combination test, with brand names including the Abbott ARCHITECT HIV Ag/Ab Combo, Bio-Rad GS HIV Combo Ag/Ab EIA, and Roche Elecsys HIV Duo. If you are asking your doctor for an HIV test, simply requesting "an HIV test" is sufficient, as they will order the appropriate screening test. Older test names you may encounter include ELISA or EIA for screening and Western blot for confirmation.

What is the most accurate HIV blood test?

Laboratory-based fourth-generation antigen/antibody combination tests combined with the HIV-1/HIV-2 differentiation immunoassay (for confirmation) provide the most accurate diagnostic results. These tests achieve sensitivity and specificity exceeding 99.5% after the window period. Nucleic acid tests (NAT/PCR) are the most sensitive individual tests and can detect HIV earliest, but they are typically used for specific situations rather than general screening. The combination of a fourth-generation screening test followed by appropriate confirmatory testing provides the highest overall diagnostic accuracy.

How is the HIV blood test performed?

Most HIV blood tests involve drawing a small sample of blood from a vein in your arm using a needle. The sample is sent to a laboratory for analysis. Rapid HIV tests can use blood from a finger prick or oral fluid and provide results in about 20 minutes. At-home tests like the OraQuick use an oral fluid swab that you perform yourself. The specific method depends on which test your provider orders or which testing option you choose.

Do I need to fast before an HIV blood test?

No. Fasting is not required for HIV blood tests. Unlike glucose or lipid tests, HIV tests detect antibodies, antigens, or viral genetic material, none of which are affected by recent food intake. You can eat and drink normally before your HIV test. However, if your provider is ordering other blood tests at the same time (such as a metabolic panel or lipid panel), those may require fasting. Ask your provider whether any other tests being ordered have preparation requirements.

How long does it take to get HIV blood test results?

Rapid HIV tests provide results in approximately 20 minutes. Laboratory-based antibody and antigen/antibody tests typically return results in 1 to 3 business days. Nucleic acid tests (NAT) may take 1 to 5 business days. At-home self-tests like OraQuick provide results in 20 minutes, while home collection kits that send samples to a laboratory typically return results within 3 to 7 business days.

What does a positive HIV test mean?

A positive result on an initial HIV screening test is considered preliminary and must be confirmed with additional testing. If the confirmatory test is also positive, it means HIV infection has been detected. This is not an AIDS diagnosis. HIV is a manageable chronic condition, and with early and consistent antiretroviral therapy (ART), people with HIV can live long, healthy lives. Modern treatment can reduce the viral load to undetectable levels, at which point HIV cannot be transmitted to sexual partners (Undetectable = Untransmittable, or U=U). If you receive a positive result, your healthcare provider will guide you through next steps including confirmatory testing, treatment options, and support resources.