What are the Available HIV tests?

What are the various HIV tests available?

Many different strategies are used to detect HIV in the blood. The following from blood can be used to detect HIV infection –

  1. Antibodies in the blood to HIV virus: Antibodies are those chemical substances produced in the body to fight a germ/infection. It takes about 1-3 months for the body to be able to produce these antibodies when infected with the HIV virus. So, these tests will not be positive for before 1 month of exposure and may be falsely negative till up to 3 months. These are the most commonly used tests to diagnose HIV infection. They are recommended to be taken after 6 weeks of exposure. Western blot is also an antibody-based test which is used to confirm the diagnosis of HIV infection when in doubt.
  2. The viral proteins or antigens: Antigens are those foreign substances belonging to viruses or germs which induce production of antibody in the body. Example: p24 protein antigen of the HIV virus. After the HIV infection it takes about 2 weeks to 1 month for the p24 antigen to be released in the blood. So, any tests before this time will not be positive. These antigens also disappear 2-3 months after infection. So, if a test for p24 is performed after 2-3 months, these may also be negative. This is not a commonly used test on its own. It is commonly combined with the antibody detection tests so that the infection can be detected both early and late during infection.
  3. The viral genetic material: This involved detecting the RNA or DNA of the HIV virus. The Viral RNA can be detected as early as 3 days but usually between 7-14 days. This is not routinely used for diagnosis of HIV due to many reasons including cost, time and complexity.

What is the benefit of an HIV test?

Knowing your HIV status can have 2 important benefits.

  • If you learn that you are HIV positive, you can take steps before symptoms appear to access treatment, care and support, thereby potentially prolonging your life and preventing health complications for many years.
  • If you know that you are infected, you can take precautions to prevent the spread of HIV to others.

How frequent is frequent?

This depends on a lot of factors including your number of partners, your frequency of sex, your use of condoms or PrEP, your use of injectable drugs, your contact with commercial sex workers etc.
There is no one size fits all approach here. A schedule can be worked out by your doctor after knowing your lifestyle. Be honest with your doctor about your sexual practices otherwise he/she will not be able to help you.
A rough guide for the testing is –

  1. A screening test for HIV every 6 months to 1 year.
  2. Once a year tests which screen for Syphilis, Chlamydia and Gonorrhea. These can be more frequent, like once in 3-6 months, if you are sexually more active and often have unprotected sex or involve in other high-risk activity.

How long after a possible exposure should I be tested for HIV?

The time it takes for a person who has been infected with HIV to seroconvert (test positive) for HIV antibodies is commonly called the “Window Period.”
The California Office of AIDS, published in 1998, says about the window period: “When a person is infected with the HIV virus, statistics show that 95-97% (perhaps higher) of all infected individuals develop antibodies within 12 weeks (3-months).”
The National CDC has said that in some rare cases, it may take up to six months for one to seroconvert (test positive). At this point the results would be 99.9% accurate.
* What does this mean for you?
The three-month window period is normal for approximately 95% of the population. If you feel any anxiety about relying on the 3-month result, by all means you should have another test at 6 months. (Source: San Francisco AIDS Foundation)

What does undetectable mean?

Undetectable is a stage one arrives at during the treatment where the viral copies are so few in the blood that common tests cannot pick up the virus. This stage can be reached when one is very regular with the treatment for at least 6 months. The viral copies are usually less than 50 per millilitre when one is said undetectable.
There are a lot of advantages of being undetectable-

  1. Since the level of circulating virus is very low in the blood the body is prevented from the harm HIV is causing. This means longer, healthier and near normal life.
  2. By being undetectable, there is very little chance of spreading HIV to your sexual partners through sex.

What undetectable does not mean is that-

  1. It is not a cure from HIV. HIV is still in the body. HIV tests are still positive, and ART must be continued for life time. But by continued ART, you can maintain the undetectable status.
  2. It is not a permanent status. Viral loads can fluctuate based on many factors and one needs to be regular in getting his viral loads checked (like every 3-6 months).
  3. It does not mean one can have sex without condoms. Because the viral loads can fluctuate and there is a risk of other STDs when condoms are not used.