HIV testing

How to check for HIV

Human Immunodeficiency Viruses (HIV) are two species of Lentivirus that can infect humans. If left untreated in the body, over time, they cause progressive failure of the immune system. As a result, life-threatening opportunistic infections and cancers can occur. This late stage of HIV infection is termed Acquired Immunodeficiency Syndrome (AIDS).

HIV is spread through contact of infected bodily fluids through mucous membranes, broken skin or wounds. Most people who get HIV get it through anal or vaginal sex, or sharing needles, syringes, or other drug injection equipment. HIV can also be transmitted from a mother to her baby during pregnancy, birth, or breastfeeding. However, because of advances in HIV prevention and treatment, it is possible for spread and infection to be mitigated.

There are a few ways that a person can test for HIV.

The most common test that is done is an antibody test. The antibody to HIV is only produced if you have been previously exposed to HIV before. Therefore, if you have the antibody to HIV, it is likely that you have been exposed to HIV at some point in time in your life. We can test for the HIV antibody from a blood sample, or from a sample of cells taken with a swab from inside your cheek. The HIV antibody test is commonly done together with a p24 antigen test. This combination testing is commonly termed a 4th generation HIV test. The p24 antigen is a distinctive HIV antigen; a structural viral protein makes up most of the HIV viral core, or ‘capsid’. Again, it will only be present in your blood if you have previously been exposed to HIV. If the doctor sends your blood to a laboratory, it is likely they use a technique known as ELISA/EIA (enzyme-linked immunosorbent assay/enzyme immunoassay). An antibody test or a 4th generation test can also be done as a rapid, point-of-care test, where all we need is a small amt of blood and 20 minutes wait time.

You might also have heard of a western blot test. A western blot is a different technique that laboratories use to test for HIV antibodies in a person. A western blot is usually used to confirm a positive ELISA/EIA result.

There are also tests which test for the HIV virus itself. This is termed a HIV PCR RNA or HIV viral load. This test can tell the doctor the concentration of HIV virus in a person’s blood. This test is also used to monitor how effective medications are in a HIV-positive patient undergoing treatment. This test is usually more expensive than the other investigations.

Window Period For HIV

The window period is time between HIV infection and the point when the test will give an accurate result. During the window period a person can have HIV and be very infectious but still test HIV negative. It is difficult to say exactly when the best time to test for HIV is, but in general, we can test for HIV as early as 10 days after exposure with a viral load test. For combination antibody testing, the result is usually deemed definitive 4-6 weeks after exposure.

If you feel that you might have been exposed to HIV, see your doctor early and the doctor can advise you on your risk, the best time to test and the type of test that is necessary. Also remember to practice safe sex to reduce your risk of contracting not just HIV, but other sexually transmitted infections as well.


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