AIDS\HIV INFECTION: DIAGNOSIS
The ultimate test for HIV infection and AIDS is a positive blood test. A sample of blood is sent to a laboratory where they test for evidence of HIV ‘antibody’. Antibody is the stuff that the body makes when it has tried to fight a particular bug. For example, if you have had chicken pox it would be possible to find antibody to the chicken pox virus in the blood stream. If there is HIV antibody in the blood it will prove that the body has been in contact with that particular virus, and that person is said to be ‘antibody positive’. We do not yet have a blood test which identifies the presence of the actual bug; we can only identify the antibodies to it. We know that with HIV this means that the person not only has antibodies to the virus, but also active, infective virus floating around the blood stream.
The problem with the blood test is that it will generally take up to three months after infection for the antibodies to show in the blood. This means that the infective virus particles may be in the blood, but the tell-tale antibody isn’t. It means that a person may feel well, be antibody negative on a test, but be infected and able to infect others. This period of being infective, and antibody negative is referred to as the ‘infective window’ or ‘window period’.
It is recommended that people have two tests, at least three months apart, with no ‘high-risk activity’ (doing things likely to put you at risk of catching the bug, outlined later) between tests if they want to be sure they are not infected. This makes sense, as it allows for the window period. Some researchers and clinicians have recommended allowing for a six-month window period, as it may take longer for some people to develop antibodies.
Contrary to the belief of some people, blood is not routinely tested for HIV whenever a blood test for anything else is taken. Guidelines for the handling of HIV testing have been suggested for Australian doctors, because the nature of the disease means that extra concerns about confidentiality and other ethical issues are raised. In Australia, doctors who order the test should do so at the request, or at least with the permission, of the patient. It should not be undertaken without a discussion of the test, its limitations, and what the consequences of a positive and negative result would be. The result should be given, in person, only to the person who was tested, and the result should remain confidential. Many insurance companies now request HIV results for insurance policies, and this is only done with written authorisation from the patient.
The stage of the disease (where along the line from ‘infected and well’ to ‘terminally ill’) in a particular person is worked out by a number of classifications doctors use. The stage of the disease is usually monitored by testing the numbers and function of certain white blood cells, and clinical findings.
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