Jan 20, 2010
Ultra-fast, accurate identification of HIV 1 (Group M and Group O) RNA, HIV 2 RNA,
Hepatitis C Virus RNA and Hepatitis B Virus DNA in human plasma from as early as 7
days post exposure.
Preliminary diagnosis of very early HIV and Hepatitis C disease is now possible at
7 days post possible exposure. This time frame was previously unavailable but utilisation of standard routine technology in a novel diagnostic style will facilitate very early diagnosis.
The technique utilises a fully automated system made by Roche and the testing method
uses polymerase chain reaction (PCR) or NAT (Nucleic Acid Amplification) to
detect miniscule amounts of viral (and the technique can be applied to bacteria) genetic material.
The technique was invented in the early 1980's by a Dr Kary Mullis, who later won the Nobel Prize for the invetion of such an elegant molecular biological technique.
Initially, the test was cumbersome and required intensive well-trained technicians to run it.
In addition, the cost of running the test, partly because of the numbers of people involved was high.
Automation via the Roche Taq Multiplex device has enabled highly sensitive, highly specific,fully automated testing to be run on human blood with the detection of HIV-1and HIV-2 possible from 6 or 7 days post exposure; detection of Hepatitis C from 6 or 7 days post exposure and Hepatitis B virus from 20 days post exposure.
The technique has had most application so far in terms of screening the human blood supply from blood donors and has reduced the numbers of inadvertent contamination with HIV and Hepatitis C virus very considerably. The technique is also employed in organ donation settings where organs to be donated are screened for the HIV-1, HIV-2,Hepatitis C and Hepatitis B viruses.
Thinking laterally and working with The Doctors Laboratory ( a major global referral laboratory in London and CPA, UKNEQUAS, WEQAS, ISFG and EMON approved for quality, robustness and high standards), we have collaborated to apply the blood and tissue screening, ultra-high sensitive technique to beginning the diagnostic process for the
The process works as follows. We take a measured amount of blood sufficient to run the three NAT tests for HIV-1 and HIV-2; Hepatitis C virus and Hepatitis B virus. We can also include syphilis IgG and IgM within that screen. The test is performed using the Roche platform and runs on the "sample in, results ou" technique
which reduces chances of contamination of product etc to zero. Should a positive sample be produced the whole specimen is drilled down to identify the virus producing the positive result and further confirmatory tests are performed.
The outcome is a highly sensitive, highly accurate detection methodology for detection of the identifed viruses. The turnaround time is swift, taking a maximum of 4 days.
This has great potential in terms of 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 targetingin 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 p24antigen which reduces the HIV 1 detection interval by a week or so. In symptomatic individuals the combination of HIV 1 and HIV 1p24 antigen has successfully identified HIV positive individuals at 12 days post infection. Co-infection with
Hepatitis 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 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 7 days post infection. Similarly, early identification of hepatitis B will be possible with reduction of the window period for this illness to 20 days.
Labels: 7 day HIV test, Hepatitis B virus DNA, Hepatitis C RNA test from 7 days, HIV PCR test, Nucleic Acid Amplification technique, polymerase chain reaction, ultra-fast HIV 1 and 2 RNA testing London
Posted by Freedomhealth