What Test Is Used to Confirm an HIV Diagnosis? Understanding HIV Confirmation Tests

Knowing your HIV status is crucial for your health and the health of your partners. If you suspect you may have been exposed to HIV, or if you just want to be proactive about your health, getting tested is the first and most important step. An initial positive HIV test can be concerning, but it’s vital to understand that a diagnosis of HIV is confirmed through specific follow-up testing. So, What Test Is Used To Confirm A Diagnosis Of Hiv? This article will explain the process of HIV testing, focusing on the confirmatory tests that ensure an accurate diagnosis.

Why Confirmation is Essential After an Initial Positive HIV Test

When you take an HIV test, particularly a rapid test or a self-test, a reactive or positive result is considered preliminary. This means the initial test suggests the presence of HIV antibodies or antigens, but it’s not definitive. A confirmatory test is always needed to ensure accuracy and rule out any possibility of a false positive result.

False positive results, while not common, can occur with initial HIV screening tests. These can be due to various factors, including technical issues with the test, certain medical conditions, or even pregnancy in some cases. Therefore, to provide a definitive diagnosis and to begin appropriate care and treatment, a more specific and reliable test is required to confirm any initial positive finding. This is where HIV confirmatory tests come into play.

Types of HIV Tests and the Role of Confirmatory Testing

To understand which test confirms an HIV diagnosis, it’s important to first understand the different types of HIV tests available and how they work. HIV tests fall into three main categories: antibody tests, antigen/antibody tests, and nucleic acid tests (NAT).

Antibody Tests

Antibody tests are the most common type of HIV screening test. They look for antibodies to HIV in your blood, oral fluid, or urine. Antibodies are proteins produced by your immune system to fight off infections, including HIV. It can take the body some time to produce these antibodies after infection, which is known as the window period.

Rapid Antibody Tests: Many point-of-care tests and HIV self-tests are antibody tests. These provide quick results, often within 20-30 minutes, using blood from a finger prick or oral fluid. While convenient and readily accessible, a positive result from a rapid antibody test must be confirmed with a follow-up test.
Laboratory Antibody Tests: These tests are performed on blood drawn from a vein and sent to a lab. They are more sensitive than rapid tests in detecting antibodies but still require confirmation if positive.

Alt: Diagram illustrating the window period for HIV antibody tests, ranging from 23 to 90 days post-exposure.

Antigen/Antibody Tests

Antigen/antibody tests, also known as combination tests or fourth-generation tests, look for both HIV antibodies and antigens. Antigens are parts of the virus itself that trigger an immune response. A specific HIV antigen called p24 appears earlier in the infection than antibodies. By detecting both antigens and antibodies, these tests can detect HIV infection earlier than antibody tests alone.

Laboratory Antigen/Antibody Tests: These are the recommended initial tests in laboratory settings and are widely used in the United States. They involve drawing blood from a vein. Like antibody tests, a positive result on an antigen/antibody lab test requires confirmation.
Rapid Antigen/Antibody Tests: There are also rapid antigen/antibody tests available that use blood from a finger prick. These offer faster results than lab tests, but again, a positive result necessitates a confirmatory test.

Nucleic Acid Tests (NAT)

A Nucleic Acid Test (NAT), also known as an HIV RNA test or viral load test when used to measure the amount of virus, is the confirmatory test used to confirm a diagnosis of HIV. NATs look for the actual HIV virus in the blood, rather than antibodies or antigens. This makes them the most accurate and sensitive tests, capable of detecting HIV very soon after infection – typically within 10 to 33 days after exposure, which is earlier than antibody or antigen/antibody tests.

NAT as a Confirmatory Test: When an initial screening test (antibody or antigen/antibody test) comes back positive, a NAT is usually performed on the same blood sample to confirm the diagnosis. If the NAT detects HIV virus, the initial positive result is considered a true positive, and an HIV diagnosis is confirmed.
NAT for Early Detection: NATs are also used in specific situations where very early detection of HIV is needed, such as for people who have had a recent high-risk exposure and have symptoms of acute HIV infection, or when initial antibody or antigen/antibody tests are negative but there is still a high suspicion of infection.

Alt: Chart comparing the window periods for different types of HIV tests, highlighting NAT as having the shortest window period (10-33 days), followed by antigen/antibody lab test (18-45 days), antigen/antibody rapid test (18-90 days), and antibody test (23-90 days).

In summary, while antibody and antigen/antibody tests are crucial for initial HIV screening, the Nucleic Acid Test (NAT) is the definitive test used to confirm an HIV diagnosis after a preliminary positive result.

Understanding Test Results and the Confirmation Process

Knowing what to expect after receiving your HIV test results is essential, particularly if you receive a preliminary positive result from a rapid test or self-test.

Positive Initial Screening Test Result

If your initial HIV screening test, such as a rapid antibody test or a rapid antigen/antibody test, comes back positive or reactive, it’s important to remain calm and understand the next steps. A positive result on a screening test is not a diagnosis of HIV. It means that further testing is required to confirm whether you have HIV.

Follow-up Confirmatory Testing: Typically, if you test positive on a rapid test in a clinic, community program, or with a self-test, you will be directed to a healthcare provider or lab for follow-up testing. If you are tested in a healthcare setting or lab, and your initial antigen/antibody test is positive, the lab will automatically conduct a confirmatory NAT on the same blood sample.
The Confirmatory NAT: The NAT will determine if HIV virus is actually present in your blood. If the NAT is positive, it confirms the HIV diagnosis. If the NAT is negative or undetectable, and depending on the specific situation and tests used, further investigation or repeat testing after the window period may be recommended by your healthcare provider.

Negative Initial Screening Test Result

A negative result on an HIV test is generally good news. However, it’s crucial to consider the window period. If you were recently exposed to HIV (within the last 90 days for antibody tests, or within the window period specific to the test used), a negative result might be a false negative.

Testing After the Window Period: If you had a potential exposure, and your initial test was negative, it’s recommended to get retested after the window period for the type of test you took to ensure an accurate result. If you have no further exposures during this period and your repeat test is negative, you can be confident that you do not have HIV.

How to Get Tested and Confirmed

Access to HIV testing is widely available. Here are several ways to get tested and ensure proper confirmation if needed:

Healthcare Provider: Your primary care doctor can order HIV tests. This is a confidential and reliable way to get tested and receive follow-up care if necessary.
HIV Testing Centers and Clinics: Many local health departments, community health centers, and specialized HIV testing centers offer free or low-cost HIV testing. These centers are often staffed with counselors who can provide support and answer your questions. You can find testing locations using online locators such as gettested.cdc.gov.
Home HIV Self-Tests: Self-tests are available at pharmacies and online, allowing you to test privately at home. Remember that a positive self-test result requires confirmation from a healthcare provider.
Mobile Testing Units: Some areas have mobile HIV testing units that bring testing services to communities, making it even more accessible.

Regardless of where you choose to get tested, ensure that if your initial screening test is positive, a confirmatory NAT is performed to finalize the diagnosis.

What a Confirmed HIV Diagnosis Means and Next Steps

Receiving a confirmed HIV diagnosis is a significant life event. It’s normal to experience a range of emotions. However, it’s crucial to remember that HIV is now a manageable condition, not a death sentence.

Access to Treatment: With effective antiretroviral therapy (ART), people with HIV can live long and healthy lives. ART works by reducing the amount of HIV in the body (viral load) and allowing the immune system to recover. The goal of treatment is to achieve an undetectable viral load, which means the level of HIV in the blood is so low that standard tests cannot detect it. Undetectable also means untransmittable (U=U) – people with HIV who achieve and maintain an undetectable viral load cannot sexually transmit HIV to their partners.
Comprehensive Care and Support: Following a confirmed diagnosis, it’s essential to connect with HIV care services. This includes medical care, counseling, support groups, and resources to help you manage your health and well-being.
Prevention for Partners: If you test positive for HIV, it’s important to inform your current and past sexual partners and anyone with whom you’ve shared needles, so they can get tested and access care if needed. There are also effective prevention strategies for partners who are HIV-negative, such as pre-exposure prophylaxis (PrEP).

Conclusion

Knowing your HIV status is an act of self-care and responsibility towards your partners. While initial HIV screening tests are readily available and provide quick results, it is the Nucleic Acid Test (NAT) that serves as the confirmatory test used to confirm a diagnosis of HIV after a preliminary positive result. Understanding the importance of confirmatory testing, the types of tests available, and the steps to take after testing positive empowers you to make informed decisions about your health and access the care and support you need to live a healthy life with HIV. If you have any concerns about HIV or your risk, don’t hesitate to get tested. Early detection and treatment are key to managing HIV and protecting your health and the health of others.