Early HIV & Hepatitis Detection Tests

There are two testing options now available for those who are worried about having contracted HIV and who want to be tested before the HIV 1&2/p24 Antigen 28 day standard.

HIV/ Hepatitis B and C Screen by PCR/ NAAT

Ultra early and exquisitely accurate HIV-1 (Groups M and O) RNA; HIV-2 RNA; and Hepatitis B and C RNA testing is available from The Wright Practice.

This tests for exposure just 10 days after a sexual encounter.

Accuracy is more than 99%.

The technique utilises a fully automated system made by Roche and the testing method uses a technique called polymerase chain reaction (PCR) or NAAT (Nucleic Acid Amplification) to detect minuscule amounts of viral genetic material. The technique can be and is applied to bacterial diseases also.

Automation via the Roche Taq Multiplex device has enabled highly sensitive, highly specific and fully automated testing to be run on human blood with the early detection of HIV 1 and HIV 2 and Hepatitis B and C possible from 10 days post-exposure.

The technique has had most application in terms of screening the human blood supply from blood donors and has reduced the numbers of inadvertent contamination with HIV and Hepatitis B & C virus very considerably. The technique is also employed in organ donation settings where organs to be donated need to be very quickly screened for HIV 1; HIV 2, Hepatitis C, and Hepatitis B viruses.

The outcome is a highly sensitive, highly accurate detection methodology for detection of the identified viruses. The turnaround time is swift, taking a maximum of 5 working days.

This allows the early identification of newly infected HIV-positive patients. and also to allow those who think they may have been infected to relax and enjoy considerable peace of mind.

The identification of patients newly infected with HIV is important because it presents several interventional opportunities. It allows for very early identification of newly infected HIV positive people which provides the opportunity to anticpate and if necessary terminate by the use of anti-retroviral drugs the seroconversion illness; to mitigate the chances of that infection being transmitted unknowingly onwards to another individual; possibly to alter the course of the HIV illness by allowing a very early intervention to limit immune system damage should early intervention at the very early stage be proved to be beneficial.

In the FDA Workshop on Implementation of Nucleic Acid Testing as long ago as 1999, a Dr Busch identified the well-known phrase, the “window period” as being of critical importance in identifying and targeting in terms of NAAT.

The window period for HIV 1 and Hepatitis C virus has to date depended very largely on the sensitivity of the HIV 1 and Hepatitis C antibody detection devices.

This was improved on for HIV by the introduction of parallel screening with HIV 1 p24 antigen which reduces the HIV 1 detection interval by a week or so. In Europe we have had this test, commonly referred to as the HIV DUO test or HIV COMBO test for many years. In symptomatic individuals the combination of HIV 1 antibodies and p24 antigen has successfully identified HIV positive individuals at 12 days post infection. Co-infection with Hepatitis B & C and HIV has presented a diagnostic conundrum with occasional delayed sero-conversion – a group referred to as “immuno-silent”.

Studies on blood taken sequentially and regularly from people in the evolving phases of HIV and Hepatitis B & C diseases have given valuable information on the window period and which markers appear at what stage. Dr Busch coined the phrase “the eclipse period” which I think is a very elegant way of describing the time between physical transfer of infection to a person and the time when current testing methodologies can identify the illnesses.

Almost invariably when a person has been exposed to HIV then by the time they have symptoms they are already in a “viraemic” phase where there is lots of virus detected.

With lots of virus comes lots of core viral proteins-referred to as p24 antigen and so the combined HIV-1 and HIV-1 P24 antigen test is virtually always positive in the symptomatic patient.

So coming back to Dr Busch and his “eclipse phase”, this is the time period we are interested in detecting and the blood and organ donation services across Europe and the USA have utilised highly sensitive NAT techniques to identify early infection to halt contamination of the transfusion blood supply and transplanted organs.

Use of Nucleic acid Amplification Testing or PCR will reduce the window period, currently contained in the “eclipse phase” as described above, and allow early identification of newly infected HIV positive and Hepatitis C positive individuals at 10 days post infection. Similarly, early identification of hepatitis B will be possible with reduction of the window period for this illness to 20 days.

Rapid Xpert HIV-1 RNA Viral load

Originally formulated to assess the Viral load of a new HIV diagnosis or the efficacy of Antiretroviral medication, it is now a highly effective test to detect early HIV infection.

This can be done using Nucleic acid-based molecular diagnostic assays and has an accuracy comparable with the HIV/ Hepatitis B and C Screen by PCR/ NAAT at 7 days after potential HIV exposure.

This does not test for the HIV 2 virus, however.