PCR tests, antibody tests and
May 28, 1999
Hello Dr. Holodniy:
This question will hopefully be a slightly different twist from the usual "window period" question :-) Sorry for the length.
I wrote previously ( I am the one taking immuno-suppressive medications who may or may not develop antibodies) and I have some good and bad test results to report.
The Good =>
**DNA PCR QUALITATIVE (Quest Diagnostics, San Luis Obispo) supposedly down to 10 copies/ml NOT detected at 7.5 weeks after possible exposure date.
**HIV-1 Antibody (California Dept. of Public Health) NON-reactive at 8 weeks.
**RNA PCR QUANTITATIVE (Stanford University Hospital) supposedly down to 20 copies/ml NOT detected. at 8.5 weeks after possible exposure.
The Bad =>
As a check on whether I would develop antibodies, I checked on vacinations for Hepatitis A, B that I received last year. I did successfully make antibodies against Hep. B but not for Hep A (at 1 year after the second shot). My doctor was a bit surprised, I think, since apparently 99% of people are successfully vaccinated.
As an aside to all those readers of this forum who may be concerned whether they develop antibodies within the six month window, they may try running the experiment of having themselves vaccinated with one of the various viral vaccines that exist (assuming no prior infection/vaccinations) and checking whether antibodies develop. I haven't read anything that would suggest that antibody develpment against HIV is any different than for other viral infections, so I would think this experiment may prove useful.
If nothing else, it will be a good prophylactic measure and even the insurance companies may approve as vaccination of large groups is probably still cheaper than treatment of the few who would be infected without the vaccination, not to mention less suffering on the part of those who may avoid infection.
On another aside, I have a theory about why "13month" man eventually tested positive on ELISA but had undetectable viral load tests for a long time.
There is a paper put out by Chiron titled "HIV-1 Non-B subtypes: A Global Issue in Test Acuracy" which points out increasing prevalence of non-B subtypes of HIV-1 in the US and Western Europe. It cites 20% prevalence of Non-B subtype in London, the number one destination of American tourists and 16% non-B in France.
The main thrust of the paper is that the RT-PCR assay may under-estimate the viral load of non-B types by factor of 100 to 1000 (2 to 3 logs). So someone who might be infected with viral load 10,000 (non-B type) may not be detectable on the standard viral load test and perhaps not on the DNA PCR Qualitative as well, with detection range say 20 copies/ml. (I found the article on the web at www.chiron.com, I think). I don't have the URL handy, but I can post it next time, if you have difficulty finding it.
Now bear in mind that Chiron may have an axe to grind in that their viral load bDNA assay can detect non-B types because they look at more points on the viral genome, but it is interesting none the less.
I suppose that the only definitive test is the Abbot MO2 Elisa antibody test,that detects all known variants of HIV-1 and HIV-2 but is apparently not FDA approved yet, assuming that one makes antibodies of course. Any update on when this test will be available ?
Anyway, I almost forgot to ask my question:
Given that antibody development in my case may be hit or miss (I will certainly get another datapoint when I repeat the vaccination process for Hepatitis A and check whether I develop protective antibodies), do you recommend that I should take another PCR Qualitative test further down the road at 3 or 6 months in addition to the usual 3 month or 6 month antibody test ?
Thankyou as always for your help to me and so many other readers of this forum. It is greatly appreciated.
Response from Dr. Holodniy
Good synopsis. I don't think you need more testing. the PCR based tests will detect the presence of the virus, so antibodies are not an issue. The issue with the subtypes and PCR is a quantitative one. Thus, it should be fine for qualititative analysis because they maximize the sensitivity and lose the quantitation effect. MH
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