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Yoxly Awesome Contributors

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Medically Reviewed by:

Dr Danae Maragouthakis

HIV (or human immunodeficiency virus) is a sexually transmitted infection (STI) which causes a lot of anxiety. Testing for HIV can be a confusing process, with many different sampling methods and types of tests. It’s sometimes tricky to know if you are taking the most accurate HIV test and if you’re taking it at the right time. 

What Is HIV?

HIV is primarily spread through semen, vaginal secretions, and blood. HIV attacks the immune system and, if left untreated, eventually renders the body unable to fight off infections – known as acquired immunodeficiency syndrome (AIDS) or late-stage HIV.

If you’re worried you may have HIV, it’s best to get tested. The type of test determines how soon after infection the virus can be detected. There are lots of different types of HIV tests, with different wait times and levels of accuracy, which can be confusing. So, let’s explore how each test works in more detail.

How Do HIV Tests Work?

HIV tests can measure three markers: antigens, antibodies, and RNA.

Antigens are found on the outside of bacteria, cells, or viruses. Once infected, antigens from that specific bug can be detected in the body after a few days or weeks. For HIV, the main antigen is called p24, which is detectable within two to four weeks after initial infection. It may become undetectable again after a variable period of time. 

Antibodies are secreted by your body to fight foreign substances, like viruses and bacteria. They are specific, meaning that the antibodies against HIV differ from those made to fight other viruses, and they can take several weeks after the initial infection to be detectable. When it comes to HIV, two antibodies are tested for: IgM and IgG. IgM is detectable first, appearing within just a few weeks; however, it becomes undetectable later on in infection. IgG appears later and continues to increase in untreated infection. 

RNA in viruses is similar to DNA in humans: it contains their genetic material. These genes store all the information a virus needs to create copies of itself as the infection progresses. HIV RNA can be found in the blood within ten days after infection. HIV RNA tests are not recommended or licenced for use for initial HIV screening, as they are likely to give false positive results.

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What Is 4th Generation HIV Testing?

Fourth generation HIV testing involves looking for both HIV antigen (p24) and both types of HIV antibodies (IgG and IgM). The p24 antigen is found in the blood before the body has had time to make antibodies, so 4th generation tests can often detect HIV infections earlier than other tests – sometimes after just a few days. Because the p24 antigen and the IgM antibody aren’t detectable forever, testing for the IgG antibody (which persists) ensures an accurate and reliable test. 

Using 4th generation testing methods, up to 99% of infections are detected 45 days after contracting HIV.

Third generation tests only test for HIV antibodies (IgG and IgM). A 3rd generation test is accurate 60–90 days after a potential exposure. 1st and 2nd generation tests only check for HIV IgG antibodies, and are not widely used.

At Yoxly, our sexually transmitted infection test kits use 4th generation HIV testing methods, which are most accurate from 45 days after potential exposure to HIV. 

When to Get Tested for HIV With a 4th Generation Test

If you are sexually active, it’s a good idea to test yourself for STIs, including HIV ,every year. If you’re regularly having condomless sex with new partners, it’s best to get tested every three months.

Remember, even if you contract HIV, there is a window period during which you might still test negative. That’s why the timing of testing is important. For 4th generation tests, the window period for HIV is 45 days. Therefore, testing at least 45 days after potential exposure is important to ensure the most accurate results.

Yoxly’s 4th generation at-home HIV testing kits reliably detect 99% of cases 45 days after exposure. Try taking one of our STI tests in the comfort of your own home, with results delivered to your inbox in just a few days.

How to Take a 4th Generation HIV Test

There are several ways to take a 4th generation HIV test. 

  1. Self-sampling

Self-sampling is usually performed at home using a finger prick test. You collect a few drops of blood from your fingertip into a container using a small lancet. The container is then posted to a laboratory for testing. Results are given at a later date via email, an online portal, or telephone call.

  1. Point-of-care testing

Point-of-care testing (POCT) involves self-sampling at a safe place, such as a community hub, charity, or clinic. You will usually get the result within 20 minutes, and there will be people present to support you in case of a positive result.

  1. Sexual health clinic STI screening

This is often part of a more comprehensive sexual health screen, which tests for several STIs using a blood sample and other types of samples (like urine, vaginal swabs, rectal swabs, or oral swabs). A blood sample is taken from a vein in your arm by a healthcare professional and sent to a laboratory for testing. 

How Accurate Are 4th Generation HIV Tests?

Fourth generation HIV tests are extremely accurate when taken at least 45 days after potential exposure, and will detect 99% of HIV infections. If a test is taken sooner than 45 days after possible exposure, it may be less accurate and more likely to give you a false negative. If you tested sooner than 45 days after you might have been exposed to HIV, we recommend repeating the test after 45 days have passed. 

4th Generation HIV Testing With Yoxly

Taking a 4th generation HIV test with Yoxly is quick and easy. A 4th generation HIV test is included in our Standard and Comprehensive kits. Within the kit are detailed instructions on how to take your sample and how to access your results. Your results are typically available one to two days after we receive your sample and can be accessed via an online portal. Finally, 4th generation HIV test results are accurate just 45 days after potential exposure to HIV. 

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Yoxly's Awesome Contributors

Yoxly's Awesome Contributors (YACs) are a diverse group of individuals who are passionate about public health, and committed to furthering our mission. Yoxly provides a platform where a variety of sexual health topics (some more awkward than others!) can be explored, in an informative and non-judgmental way. If you'd like to become one of Yoxly's Awesome Contributors, contact us!