Introduction:
HIV is a complex virus and is difficult to get rid of from the body. The timing of taking an HIV test is vital after one gets exposed to HIV. In the current era, various tests are available to screen for HIV. Regular checkups are necessary to keep oneself healthy and everyone should have some knowledge about the various screening tests one such being the test for HIV. HIV takes some time to be detected in the body.
What Is Meant by the Window Period in HIV?
The window period in HIV refers to the time interval between exposure to HIV and the time in which the HIV is detected in the body by a test. This window period can be influenced by the type of HIV test that is used.
Why Know About the Window Period in HIV?
Though some individuals may be asymptomatic or test negative for HIV during the window period, they might have acquired the HIV infection. Once a person is exposed to HIV, the person becomes highly infectious since the HIV begins to replicate at a faster pace in the body which in turn can spread the infection to others quickly. This explains the need to use an HIV prevention method like condoms, PrEP, or undetectable viral load (UVL) always.
Types of HIV Tests
Antigen refers to the foreign substances that enter the body which triggers the activity of the immune system and antibodies are those that are released by the immune system in response to foreign antigens like the HIV viruses. In HIV, the p24 antigen dwells in the body even before the antibodies develop. HIV tests can be performed on oral fluid, blood, or even on urine. The HIV tests are of three types namely:
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Antibody Test: The antibody test detects the presence of antibodies in the blood or oral fluid against HIV. This test is the most used rapid test and the only approved self-test for HIV by the U.S. Food and Drug Administration (FDA). Blood obtained from a vein for an antibody test can detect HIV more quickly than the antibody test that uses the blood from an oral fluid or a finger stick.
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Antigen or Antibody Test: These tests detect both HIV antigens and antibodies and the testing is done in a laboratory. In this test, blood is taken from the vein and is a common test carried out in the United States. A rapid antigen/antibody test utilizes the blood that is obtained from a finger stick.
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Nucleic Acid Test (NAT): This test detects the actual virus present in the blood. The blood obtained from the vein is sent to the laboratory for testing. This is called an HIV viral load test since it can predict if a person has HIV or not and determine how much virus is present in the blood. A nucleic acid test can identify HIV quicker than other tests. This is preferred in individuals who have early symptoms of HIV, those who had a recent exposure or a possible exposure, and those who have tested negative in an antigen/antibody test.
Can an HIV Test Identify the Virus Immediately Post-exposure?
It is not possible to detect HIV immediately post-exposure because of the window period. Also, the window period varies with different types of tests. A nucleic acid test is capable of detecting HIV at the earliest probably between 10 to 33 days following exposure.
Time Duration for Various HIV Test Results
The time duration is as follows:
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HIV-Self Tests: The results are obtained within 20 minutes.
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Rapid Antibody Test: This test is carried out by taking a blood sample from oral fluid or a finger stick. The results are available within 30 minutes.
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Rapid Antigen or Antibody Test: This test too makes use of the blood sample from a finger stick and the results can be derived within 30 minutes.
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Nucleic Acid Test or Antigen or Antibody Lab Test: The results may take several days to arrive.
How Long to Wait Before Taking an HIV Test?
HIV window periods can differ and a window period exists between exposure to HIV and a positive result. This is either because the body takes some time to trigger a suitable response against the infection or the virus needs some time to replicate sufficiently before it can be identified through a test. It is recommended to take an HIV test three months after a known exposure since tests taken three months after exposure are expected to be 99 % accurate.
Where Are HIV Tests Available?
HIV tests are available at various places like:
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Hospitals.
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Clinics.
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Pharmacies.
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Community clinic.
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Family planning clinic.
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Mobile sites.
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Youth clinic.
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A take-home test.
Window Periods for Other Types of Sexually Transmitted Diseases
The window period for sexually transmitted diseases other than HIV is often shorter. For instance, chlamydia has a window period of just seven days. Hence, regular screening for sexually transmitted diseases is important to keep oneself safe and healthy.
Window Period for Various HIV Tests
The window period for various HIV tests is as follows:
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Antibody Test: This test can take 23 to 90 days to determine HIV infection following exposure.
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Antigen or Antibody Test: These tests can identify an HIV infection 18 to 45 days following exposure. The antigen/antibody tests that are taken from samples obtained from a finger prick can take a longer duration to detect HIV like 18 to 90 days following exposure.
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Nucleic Acid Test (NAT): The window period of these tests is 10 to 33 days after exposure.
Precautions to Be Taken During the Window Period
The precautions to be taken are as follows:
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Post-exposure Prophylaxis (PEP): Prophylaxis is a treatment that is given or action that is taken to prevent disease. Prophylaxis is recommended for a person who is suspicious of having been exposed to HIV within the past 72 hours. The period of 72 hours is crucial since after this, the prophylaxis would not work. The duration of post-exposure prophylaxis is 28 days. Post-exposure prophylaxis (PEP) is suggested in cases of:
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Sexual assaults.
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Needle stick injury.
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Suspected exposure to HIV through sex.
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Shared needles.
Though PEP does not offer complete protection, it is highly effective in preventing an HIV infection if a person takes it at the right time. Minor side effects can occur after PEP or it can interact with the drugs that the person consumes. The side effects and the risks should be discussed with the healthcare provider. Even after PEP, the person should continue with the HIV prevention methods.
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Be Cautious: A person who is in doubt that they might have been exposed to HIV should be cautious. These cautious ways include:
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Use of condoms during sex.
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Reduce the number of sexual partners.
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Taking post-exposure prophylaxis (PEP).
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Take other tests for sexually transmitted diseases and advice the partners also to undertake the same.
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Drug needles should not be shared with others.
When to Conclude the HIV Test?
Taking two HIV tests three months apart which is the determined window period is advisable. The criteria are ‘no unprotected sex’ in between these tests and the succeeding result should be negative in both tests. Bi and gay guys who are sexually active are advised to take the tests for both HIV and other sexually transmitted diseases (STDs) once every 3 months.
How to Proceed if a Person Tests for HIV During the Window Period?
Though the patient tests negative during the window period, there is a probability that HIV was not detected by the test. Following the date of the potential exposure, another test has to be taken at the end of the window period to get an appropriate result irrespective of whether the test was done during the window period or not.
When Is One Likely to Have a Nucleic Acid Test (NAT)?
A nucleic acid test (NAT) is advised under the following conditions:
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A baby who is born to an HIV mother.
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Participation in an HIV trial.
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In case of unclear results from previous tests.
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Had a test after possible exposure but before HIV antibodies could be detected.
Conclusion:
Understanding the window period in HIV is necessary to know when to take the HIV test to determine an accurate result. In case of suspicious exposure to HIV, it is recommended to consult a health care provider since they can help the person to identify the window period and suggest when the test has to be taken to know the exact status. This also helps to know if a follow-up test is required. The best way to know the exact status of HIV infection is to take a test after the window period. It is important to follow safety precautions during the window period to avoid the spread of infection.
