The HIV test
It’s very important to have an HIV test if you think you may have been at risk of acquiring the infection. Early diagnosis and treatment can help you live a long and active life, and also helps prevent spreading the infection to others.
There are a number of different tests used to determine whether someone is infected with the HIV virus but the one most commonly used is the HIV antibody test.
An HIV test doesn’t test for whether the virus itself is present, but whether your body has made antibodies to the virus. It is usually done in two stages and involves giving a small blood sample that will be analysed in a laboratory:
Stage 1 HIV test – initial screening involves either an enzyme immune assay (EIA) or the enzyme-linked immunosorbent assay (ELISA). If the results from this test are negative, no further tests are performed. If the results are positive you will need a stage 2 HIV test.
Stage 2 HIV test – this is the “Western Blot” test which detects certain proteins in the blood sample and can confirm whether the virus is present in the body.
Test results can take up to a week or more, although some clinics offer same-day results.
Rapid HIV test – these are EIA/ELISA tests performed either on blood or oral fluids, and can give you results in just ten minutes. However, if they’re positive you will need to have the results confirmed with a Western Blot test performed in a lab. Although highly accurate, a positive result from a rapid HIV test is considered a “preliminary positive” until confirmation with a Western Blot.
Testing can be done four to six weeks after you think you might have been exposed to the infection, but sometimes it can take up to three months for the virus to develop. This is called the “window period.” Tests undertaken before these three months are not deemed reliable as antibodies may not yet have formed and therefore won’t show up on the test. You will need a repeat test a few months later to be sure of the result. An HIV test undertaken three months after possible infection is considered to be reliable.
Before having the test you will usually be offered the services of a counsellor who can explain possible outcomes and what a positive diagnosis might mean.
HIV test results
A negative test result – providing the test was undertaken three months after possible infection a negative result means that you are not infected with the HIV virus. If your test was undertaken within three months of possible infection the result is considered a “preliminary negative.” A negative test does not mean that you are immune to HIV. You can still catch the HIV virus any time if you continue to engage in “risky” behaviours, such as having unprotected sex, or sharing needles or other equipment for drug use.
A positive test result – this means that antibodies are present confirming that you are infected with the HIV virus (HIV positive). This does not mean that you have AIDS, although the infection is now with you for life and could develop into AIDS at some point in the future. You are infectious and can pass the HIV virus on to other people so must always take precautions to protect others. You may wish to find a specialist HIV doctor who can monitor your health and advise on treatment protocols. You should also tell any previous (or future) sexual partner that you are HIV positive, and anyone with whom you might have shared needles or drug equipment as they will have also been exposed to the virus and may be infected.You can tell them yourself, or ask your doctor to help you, or contact the local health department. Health departments do not reveal your name to sexual or drug-use partners, only the fact that they have been exposed to HIV.
An inconclusive (or indeterminate) HIV test result – The Western Blot test looks for antibodies to various HIV proteins. If many are found, the test is positive. If none are found, the test is negative. If only one or two types of antibodies are found the test is inconclusive (or indeterminate). This could be for several reasons:
Exposure to the virus is too recent (and the body has not yet developed a full immune response)
It is a weak reaction to other antibodies unrelated to HIV
You have had prior blood transfusions
You have an autoimmune disease such as lupus or diabetes
It is a contaminated blood sample
If your HIV test is inconclusive you will need to have a repeat test a few weeks later.