A nonreactive test means the sample did not contain HIV antibodies or antigens. This may or may not mean a person does not have HIV.

Testing for HIV can help a person receive treatment more quickly. There are different test types, and some people may receive a “nonreactive result.”

The earlier someone understands their HIV status, the better their health outcomes.

Early treatment with antiretroviral drugs can reduce a person’s risk of serious AIDS-related events by 72% and the likelihood of serious non-AIDS events by 39%.

The Centers for Disease Control and Prevention (CDC) recommends that people between the ages of 13 and 64 years receive testing for HIV at least once.

However, there are some groups of individuals who should have an HIV test more often. They include those who have been sexually active with multiple partners or those who have shared needles or syringes.

This article explores HIV testing. It will explain what a nonreactive or reactive result means and will analyze the accuracy of HIV tests.

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A nonreactive result means that the fluid sample did not contain HIV antigens or antibodies that the test aims to react to at the time of testing. It can mean a person has tested negative for HIV.

However, if an individual has a nonreactive result, it does not necessarily mean they do not have HIV.

Instead, it could mean they took the test too early to detect HIV antigens or antibodies.

If an HIV test shows a reactive or positive result, it means that the test indicated a reaction, meaning they have HIV antigens or antibodies in their blood.

Learn about early signs of HIV here.

There are two main tests for HIV screening: antigen/antibody tests and antibody tests.

Nucleic acid tests are another type of HIV test that detects the virus in the blood. However, these tests are expensive, so healthcare staff do not often use them for routine screening.

Antigen/antibody tests

Health professionals use antigen/antibody tests to look for both HIV antibodies and antigens. They take the blood from an individual’s vein or finger prick.

Antigens are substances from outside the body that prompt the immune system to act. Viruses, such as HIV, have antigens on their surface. The antigens alert the immune system to produce antibodies, specialized proteins that attack foreign invaders and keep the body safe from infections.

The primary benefit of antigen/antibody tests is that levels of p24, an HIV antigen, rise in the blood after infection, but before the immune system can produce antibodies. Therefore, these tests allow for more rapid detection of HIV infection.

Antibody tests

Antibody tests are a little more simple, detecting antibodies that the body produces in response to HIV.

People can take these tests at a doctor’s office or in their own homes using a home HIV test.

Antibody tests measure the immune response to HIV infection by testing for antibodies in blood or saliva.

Tests using blood from a vein can detect HIV infection sooner than tests using blood from a finger prick or saliva. This is due to how the virus spreads through the body.

Learn about home HIV tests here.

Receiving a nonreactive test result may mean a person has taken the test outside the correct time frame.

Window period

If someone has an HIV test immediately after contact with body fluids containing HIV, the test results can be inaccurate.

The window period is the time between when a person contracts the virus and when antibody or antigen numbers are large enough for a test to detect them. In other words, during the window period, a test may not detect HIV antibodies or antigens because there are too few of them.

Doctors refer to the time a person has enough antibodies for an accurate result as “seroconversion.”

The window period can vary depending on the sensitivity of a particular test, which antibodies or antigens the test looks for, and the individual’s biology.

Some people rapidly develop markers of HIV infection, while in others, the process may be slower.

Rapid test window period

According to CATIE, Canada’s government source for HIV and hepatitis C information, rapid HIV antibody tests have a window period of 3–12 weeks.

Rapid tests can detect HIV infection in around half of the people who have contracted HIV by day 22 following exposure. They can detect infections in 99% of people by 12 weeks.

Antigen/antibody test window period

Antigen/antibody tests detect both the viral p24 protein, an antigen, and antibodies that the body produces. Because p24 can appear more quickly than antibodies, the window period for this test is shorter.

Antigen/antibody tests can detect HIV antigens or antibodies in about half of the people who have acquired HIV after 18 days following exposure. They can detect infection in 99% of people by 44 days after exposure.

If individual tests negative after recent HIV exposure, they should request a follow-up test at the end of the window period, which will confirm the initial test results.

Individuals can transmit HIV through bodily fluids, such as:

  • blood
  • semen
  • vaginal fluid
  • anal fluid
  • breast milk

The virus enters the bloodstream in these fluids through mucous membranes, open cuts or wounds, or direct injection.

From there, the virus triggers infection of white blood cells in the immune system to create copies of itself and reproduce.

Some misconceptions about HIV are that it can spread through air and water, mosquitoes, physical contact, drinking fountains, or sharing dishes.

In truth, the virus cannot pass through healthy, unbroken skin or through saliva. It requires direct access between the bloodstream of two individuals.

Learn more about HIV transmission here.

People can lower the risk of contracting HIV by taking preventive measures. These include:

  • using condoms and other barrier methods
  • limiting their number of sexual partners
  • using sterile needles if injecting drugs
  • taking preexposure medication if individuals have a higher risk of infection
  • taking HIV medication to prevent transmission to fetuses
  • taking post-exposure medicines if necessary

Learn about antiretroviral therapy for HIV here.

Without treatment, HIV can be a serious condition. Although doctors cannot yet cure HIV, people can manage the condition with medication.

When individuals begin HIV treatment early, they are far more likely to live a full and active life with a significantly reduced risk of developing AIDS.

Early treatment depends on early detection, which highlights the importance of regular HIV testing.

For individuals who engage in high risk behavior, such as sex without a condom or sharing needles, routine HIV testing is particularly important.

However, people must remember that tests cannot detect HIV infection immediately. This is because it takes time for the body to create recognizable HIV markers.

If individuals receive a negative, nonreactive HIV test result, they should follow this up with confirmatory tests.