HIV (Human Immunodeficiency Virus)
HIV is a sexulally transmitted virus which attacks the body's immune system. A healthy immune system provides a natural defence against disease and infection. HIV infects special cells, called CD4 cells, that are found in the blood and are responsible for fighting infection. After becoming infected, the CD4 cells eventually decline and the immune system stops working. This leaves the person infected with HIV at a high risk of developing serious infection and disease.
HIV tests
Many people are aware of the need to test for HIV, although an HIV test may not show positive until three months after infection, using traditional antibody HIV tests. For this reason a donor should have two tests three months apart before donating sperm. The donor should also avoid any risk of catching the HIV virus within the three months, by either celibacy or following strict safe sex practices.
HIV Duo test or HIV 28 day test
The HIV antibody/p24 antigen Duo Test is an excellent, accurate and inexpensive HIV test that reliably detects HIV infection that occurred just 28 days prior to the test. This HIV test is known as the 'Duo' because it tests for both HIV antibodies as well as the 'HIV P24 antigen'. The HIV p24 antigen is a core HIV viral protein which becomes detectable at approximately 10 days post exposure, peaks at 16 days or so and then remains at high level for 8 to 10 weeks post exposure. It will then fluctuate over the rest of the course of the illness. HIV p24 antigen is extremely useful in combination with an HIV antibody test in determining early on whether an individual has been infected with HIV. The HIV DUO test is extremely accurate at 28 days and is now the test recommended by the new UK Guidelines on HIV testing 2008.
HIV Antibody test or HIV 90 day test
The rapid HIV test allows for results within 60 seconds via a simple prick of blood from the finger tip. This test is very accurate from 90 days post Contact for detecting HIV antibodies. This test can give immediate peace of mind if risk of infection was more than 90 days ago but is no recommended as a definitive test. It should be proceeded by a HIV Duo test for confirmation.
HIV PCR test - results from 10 days
You may also have heard of HIV PCR testing. This is the most sensitive HIV test available and aims to test for HIV 1 infection that occurred as little as 10 days prior to the test. This HIV PCR test is not 100% reliable but it is a guide for those that are desperate for some peace of mind at the earliest opportunity. We recommend that this HIV test is followed-up with an HIV Duo Test at 28 days after the suspected infection. Like the HIV Duo test, a blood sample is sent to the laboratory and the results should be with you in 5-7 working days. This test will help allay fears over the possible early symptoms of HIV. This is the most expensive of the three tests and is not normally available via NHS GUM clinics or GPs.
Which test is recommended?
The new UK Guidelines on HIV Testing published in September 2008 have emphatically recommended the use of 4th generation combined HIV p24 antigen and HIV antibody tests (HIV DUO tests) as the test of first choice, citing the very distinct benefit of the earlier diagnosis of HIV using these tests as opposed to the older 3rd generation HIV antibody tests. The 4th generation combined tests will shorten the time from infection to diagnosis by 1-2 weeks over the older 3rd generation HIV tests. The older 3rd generation tests are excellent and will still identify the majority of new HIV infections by 6 weeks.