HIV is a virus that attacks cells in the immune system. When left untreated, the virus can severely weaken the immune system over time.
Several types of tests are available to determine if someone has HIV. Testing is important both in HIV prevention and in helping people infected with the virus to seek treatment.
A person is said to be HIV negative when the test does not detect HIV. However, a negative result does not necessarily mean that they do not have HIV.
Continue reading below to learn more about the different types of HIV tests and what a negative result means.
Receiving a negative HIV test result means that the test did not detect HIV. However, a negative result does not always mean that a person is not infected with HIV.
This is because each type of HIV test has a different time period. The trial period is the time period between exposure to HIV and when the test can accurately detect that a person is infected with HIV.
If a person is tested within the trial period, the test may not be able to detect the presence of the virus and may have a negative result.
When a negative result is received during the test window period, it is important to get another test after that period has passed. This can help confirm a negative result.
In addition, exposure to HIV is possible during the window period. In this situation, HIV testing may not be accurate.
There are three different types of HIV tests, including:
An antibody test looks for the presence of antibodies to HIV in a blood or saliva sample. Antibodies are specialized proteins produced by the immune system in response to agents that cause diseases such as HIV.
Many HIV or self-tests are HIV tests. Results may be available in 30 minutes or less, depending on the type of test.
The antibody testing period is wide. It can take anywhere in between
Antigen / antibody tests
The antigen / antibody test detects antibodies to HIV as well as a specific viral protein (antigen) called p24.
A blood sample from a vein in the arm is usually used for this test. However, some rapid tests are available that use a blood sample from a finger prick.
How long it takes to achieve results may depend on the type of test. If the sample is sent to a laboratory, it may take several days to obtain results. Rapid antigen / antibody test results may be available in 30 minutes or less.
Because p24 can be found prior to the formation of antibodies to HIV, antigen / antibody tests can detect HIV infection earlier than the antibody test.
The period for the standard antigen / antibody test is
Nucleic acid tests
Nucleic acid (NAT) tests look for the presence of the genetic material of the virus in a blood sample.
NAT can detect HIV in a person’s blood anywhere in between
Blood samples for NAT are sent to the laboratory for processing. Therefore, it may take several days to get a test result.
NAT is also used after the diagnosis of HIV to detect the amount of virus in a person’s blood. This is called a viral load test.
HIV-1 is one of two types of HIV. It is the most common type of HIV in the world. In fact, it is estimated that about 95 percent of people currently living with HIV have HIV-1.
Because HIV-1 is so prevalent, most HIV tests are focused on detecting HIV-1. They include all three types of tests we discussed above.
HIV-2 is much rarer than HIV-1. HIV-2 is estimated to compensate
At the genetic level, HIV-2 is over 55 percent different from HIV-1. This means that many types of HIV tests may not be able to accurately detect HIV-2.
Testing guidelines from the Centers for Disease Control and Prevention (CDC) help address this problem. These guidelines recommend the use of an antigen / antibody test initially to detect HIV.
If this test returns positive, a second antibody test is ordered to determine if the person has HIV-1 or HIV-2. If the test results are indeterminate, NAT is done to confirm or rule out a diagnosis of HIV-1.
Due to the fact that HIV-2 is uncommon in the United States, NATs for HIV-2 are not always available. However, if HIV-2 is suspected, it exists
It is possible that the result of the HIV test may return as “indeterminate”. Simply put, this means that the test results are unclear. Tests that return indeterminate usually show a weak positive result.
This type of result is not so unusual. Researchers
There are several things that can potentially cause an indeterminate result, including if:
- the person has recently contracted HIV
- there has been an antibody cross-reaction, which may be due to things like a recent tetanus vaccination or an underlying health condition like lupus or rheumatoid arthritis
- the sample is contaminated
- a technical error occurred during testing
If the HIV test results return indeterminate, a repeat test is usually recommended.
There are some situations where a healthcare professional may recommend retesting. This includes cases of:
- negative test result within the test window period
- another potential exposure to HIV during the testing period
- indeterminate test result
Repeat risk-based testing
While it is
- men who have sex with men
- sexual partners of people living with HIV
- those who share needles
- individuals diagnosed or treated for:
Exactly when a person is tested, it may depend on the specific situation. Let’s explore some potential scenarios in more detail:
- Negative result within window period. To confirm a negative result, a healthcare professional will recommend retesting
after passing the trial period.
- Exposure during the window period. If other potential exposures occur during the test period, the healthcare professional may recommend a minimum wait
4 weeksbefore retesting, depending on the test window period.
- Indeterminate result. The test can be repeated immediately to rule out things like technical errors or sample contamination. If the results of this test are still indeterminate, a second test is usually done
2 weeks later.
There are many steps that can be taken to prevent HIV infection. These include:
- Using a condom. Using condoms during sex can prevent the transmission of the virus.
- Not sharing needles. It is important not to share needles or other injection equipment.
- Performing prophylaxis before exposure (PrEP). PrEP is a daily oral medication. It can help prevent HIV infection during sex or when using injections.
- Testing. Awareness of HIV status is a valuable tool in prevention. Testing for other STIs is also important because some STIs may increase the risk of HIV transmission. Encourage sexual partners to get tested.
- The issue of post-exposure prophylaxis (PEP). PEP is an emergency drug that can help prevent HIV after potential exposure. To be effective, it must be started within 72 hours of possible exposure.
Where to get an HIV test
There are many locations where HIV testing is available. This may include:
- health worker’s office
- sexual health clinics
- community health homes
- VA medical centers
- associated organizations in the community
- state or local health departments
- facilities for the treatment of substance use disorders
It is also possible to get a self-test that you can do at home. Some of these tests give results in less than 20 minutes. For other types of self-testing, the sample may need to be sent to a laboratory for testing.
The CDC has
There are several different types of HIV tests. Each species has a different time period for which it can accurately detect HIV infection.
A negative HIV test result means that the specific test used did not detect HIV. However, a negative result does not always mean that the person is not infected with the virus.
If an individual received their result during the study period or had another exposure to HIV during that period, retesting is recommended. The following is a scenario in which testing can be repeated in the event of an indeterminate result.
Testing is a valuable tool both to prevent the transmission of HIV and to ensure timely treatment of those infected with the virus. As such, it is important that everyone is concerned that he may have been exposed to HIV testing.