Is a Negative HIV Test at 6 Weeks Conclusive?

A potential exposure to human immunodeficiency virus (HIV) might make someone wonder how soon they can get results from a test.

Some HIV tests can conclusively detect the virus in as little as 6 weeks, but it depends on a person’s immune system and the type of test that’s done.

How accurate are HIV tests?

Some tests can detect HIV within 10 days of exposure, but detection ultimately depends on how quickly one’s immune system reacts to the virus. For some people, detection could take months.

Accuracy of a negative test result depends on a person’s body and the type of test that was used. There are a number of HIV tests that have been developed since the virus was first detected in the 1980s.

Each test has what’s called a “window period,” or the time between contact with the virus and when the virus can be detected in the body.

The window period is different for each test and person. Ask a healthcare professional about the window period for your specific test.

Newer laboratory tests work to detect antibodies to HIV as well as a viral protein called p24 (antigen) to detect an infection. Because p24 can appear before antibodies to HIV, antigen/antibody tests have a tighter window period than older tests for antibodies alone.

In fact, the newest types of antigen/antibody tests are 99 percent conclusive within 44 days of exposure.

What are the different types of HIV tests?

The window period and accuracy for HIV testing varies by test and the body’s individual immune response. The following are types of HIV tests, window periods for each, and accuracy information.

Generally, tests that use blood from a lab draw deliver accurate results sooner than tests that use finger pricks or oral swabs.

Nucleic acid tests (NAT)

This may also be called an HIV RNA or viral load test. This test looks for the presence of the actual virus in a blood sample that’s drawn in a laboratory.

With this test, the virus can be detected 10 to 33 days after exposure. This test may also help differentiate between acute and chronic HIV infections.

Antigen/antibody test

These tests are typically done in a laboratory using blood drawn from a vein.

An infection can be detected roughly 18 to 45 days after exposure. If the test uses blood from a finger prick, it may take up to 90 days to detect an infection.

Antibody tests

These tests can also be done using blood drawn from a vein. Additionally, rapid and at-home HIV antibody tests can use blood from a finger prick, saliva, or even urine.

While these tests may be able to detect antibodies to the virus in as little as 23 days, it could take up to 90 days to get an accurate result.

What are false positives and false negatives?

False-negative and false-positive test results can happen.

False-negative tests can occur when antigen or antibody levels can’t be detected in a testing sample. Perhaps the immune system didn’t develop enough antibodies to be detected at the time of the test, or the test may not have been sensitive enough to detect the levels.

If the test is done early in the window period and the result is negative, there’s a chance that a follow-up test may be positive.

If a rapid test is taken and the result is positive, a second test will be done to confirm the result.

False positives can occur and aren’t considered officially positive until the test is confirmed with a second positive test result.

When to get a second test

After exposure and a negative test, it’s best to do a repeat test after the window period closes. Some people take longer to develop antibodies against HIV. Early testing could result in a false-negative result.

It’s also a good idea to consider a repeat test 3 months after an initial exposure, or the end of the window period, and another 3 months after that to be sure the results are negative.

A repeat test is necessary if there’s another exposure after a negative test or in the window period. People who are in high-risk groups for HIV should use prevention strategies and have regular screenings — at least once per year — for the virus.

Finally, if an initial test result is positive, a healthcare professional will do a second test to confirm the result.

What to do if a test is positive

If a test is result is positive, a healthcare professional will be there to discuss next steps.

Antiretroviral treatments have improved the outlook and life expectancy for people living with HIV over the last few decades. These medications can help keep the virus in check by lowering the viral load, reducing transmission, and stopping HIV from progressing.

When to talk with a professional

An estimated 1.2 million people in the United States have HIV, and 1 in 7 don’t even know it.

Some people are at higher risk of contracting HIV than others. Risk factors include:

having vaginal or anal sex without a condom

having another sexually transmitted infection

sharing needles or syringes

Less common ways HIV may be transmitted include:

exposure though unsterile equipment during piercings, tattoos, or medical procedures

accidental needle-stick injuries

receiving contaminated injections or transfusions

Talk with a healthcare professional about prevention strategies and regular screenings for HIV.

If a test result comes back positive, a healthcare professional will discuss next steps, including a second test and a treatment plan, if that becomes necessary.

The bottom line

Regular, early HIV screening is key for preventing and treating HIV, but false-positive and false-negative tests still happen — especially in the first few weeks after infection.

Sometimes, a second test is needed to rule out false positives and false negatives.

Posted : 2024-08-29 10:49

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