Tests and Results

TESTING FOR HIV

Having an HIV test.
When you attend for a test, you will see a doctor or a specialist nurse in private. He or she will take details of your medical and sexual history and discuss with you what the test involves and what the result means. As you will see below there are three different types of test. Any test will only be performed when you have given consent for it to be done. For standard testing a small sample of blood is taken and tested in our laboratory in the clinic and a result is available within 15 minutes. Results from other tests take longer, as described below.

In some cases, you may be advised by staff in the clinic to have a repeat test at some point.

The standard HIV Antibody Test
The usual way of testing for HIV infection is by testing for the presence of antibodies to the HIV virus in a blood sample. Antibodies are specific proteins which the immune system produces in response to infections. Although 90% of individuals will have detectable antibodies as early as 6 weeks after HIV infection, in 10% of cases antibodies to the HIV virus may not become detectable in a blood sample for up to 12 weeks.

Because of this, a HIV antibody test result is only considered 99.9% accurate if at least 12 weeks have elapsed since the last sexual exposure.

The standard HIV antibody test we use at the Regents Park Clinic is the Abbott Determine HIV-1/2 rapid assay. This test detects both HIV 1 and HIV 2 and gives results within 15 minutes. The sensitivity of this test, as reported in the medical literature, is between 99.4 and 100%.

The cost of this test including consultation, is £105. It is included at no extra charge as part of an Executive health screen.

The p24 Antigen/Antibody Test (the ‘28 Day HIV Test')
P24 antigen is a protein derived from the HIV virus. It becomes detectable in a blood sample for a short period after infection (normally from 2 to 5 weeks) and rapidly becomes undetectable when antibodies to HIV start to develop. It is therefore useful in identifying early HIV infection.

In practice, a p24 antigen test is usually combined with an antibody test and this test kit is known as the Vidas HIV DUO test. This is frequently advertised as the “28 Day HIV test”. However, clinical trials have shown that on average the HIV DUO test will identify HIV infection about 1 week earlier then a standard HIV antibody test.

The cost of this test is £125 (including consultation).

The 'Early' HIV-1 Proviral Test
Another way to test for HIV infection, other then looking for antibodies, is to look for the genetic material (DNA/RNA) of the HIV virus itself in a blood sample. One such test is the HIV Proviral DNA test, which uses a complex technique called PCR to detect the virus. This test detects the presence of HIV-1 as early as 10 days following infection and does so with a sensitivity of around 96 to 99%. Because of the complexity of this test, a result is not usually available for 5 to 7 working days. The cost of this test including the consultation is £185.

Because the sensitivity of the early HIV test is not quite 100%, if you have a Proviral test you will usually be advised to have a standard HIV test after the 12 week window period has elapsed, for complete assurance.

If your HIV test is positive.....
If your HIV test result is positive, this will need to be confirmed with a further set of three confirmatory HIV tests to ensure the result is genuine and that it is not a 'false positive' result. The likelihood of receiving a 'false positive' result is around 4 in 1000 for a standard HIV test and less then 1 in 100 for a HIV-1 Proviral test. The confirmatory tests yield a result within 24 hours and cost £70.

If HIV infection is confirmed, we will advise you on what you need to do next. We will let you know about your choices for accessing HIV services, either through the NHS or privately and we will arrange referral for you if necessary.