Ann, Please thank Dr. Susan for taking so much care to clarify her opinion about PCR testing, it has been a very informative discussion topic. I was personally looking for a non-invasive way to 'simply' assertain whether my "positive turned negative" was now truly negative. It doesn't appear that the PCR test would be definitive for this purpose, (at least based on the variable testing/interpretation methods), so I probably won't be pursuing it any further. I had sent Dr. Susan's first reply to Kate; here is her response: Hi Nina,
Yes, Dr. Susan is correct that ELISA tests for the antigen of the
FeLV virus. If a patient is positive for a virus, say HIV, then the
patient's serum contains antibodies to HIV and it will bind to the HIV
antigens. For simplicity I left this out. I would like you to see how
ELISA works. If you go to www.biology.arizona.edu/immunology/activities/elisa/technique.html,
there is an animation of how ELISA works that is simple to understand.
Dr. Susan also says that she recommends IFA. If you look on the
internet several studies also agree with her, and it appears to be also
a good test. However, she does not support PCR. As I said before, lab
interpretation of PCR may be difficult and purification of feline DNA
from viral DNA, may be difficult, but not impossible and certainly
doable. PCR detects the nucleic acids of the virus. More specific
primers may be needed for PCR of FeLV, but scientifically, if you have
these primers and a patient is positive, a positve PCR means positive
infection.
I've
attached a whole bunch of web sites for you to look at. Some are
scientific papers, some are FeLV web sites, and some will help you
learn more about the science of testing for FeLV. The best suggestion
that I can give is to learn the science behind these tests. Secondly,
I have included web sites that do not necessarily agree with each
other. I can find articles in Vet journals and in scientific journals
that say that PCR is a really great thing for testing FeLV and is much
better than ELISA. I can also find journals that say PCR doesn't
really give that great of results, and to use IFA if you get a negative
test for ELISA. You have to understand that there will always be
debates in science and medicine. Noboby knows the whole story on any
virus, nor how to cure a virus. We use science and experience to find
out what works and how to make treatments better. Both Dr. Susan and I
come with our own opinions. As a vet, she will see what works in her
clinic. Other vets may come to different conclusions. As a scientist,
I have my personal faith in testing such as PCR. It's a great
technique that allows us to take a small amount of genetic material and
amplify it; However, for each specific virus we need to know the
signature sequences of the virus, to make PCR more specific.
Basically, you are only getting opinions from both Dr. Susan and I.
Nobody knows how to cure a virus- any virus- from HIV to the common
cold to FeLV. Period. Animals doctors, human doctors, and scientists
have one particularly irritating trait in common. This is arrogance.
We do know the answers to many things, but what they don't want the
public to know is that, what we do know is actually so very little in
the scheme of things. For instance, the connation of brain surgeon,
conjures up someone who is really smart. Ask a neurolgist how memory
is stored in the brain, and if he or she is honest, you will get the
answer of "I don't know." In other words, even the most basic question
in neurology still can't be answered. Never forget, there is alot we
don't know.
The
best thing I can let you know is to 1) keep asking questions, but more
importantly, start learning the science behind these questions. Do
first hand research, grab virology, immunology, and biochemistry
textbooks from a university bookstore (or you can buy them used on the
internet). Look up how antibodies and antigens work. Look up PCR and
how it works. 2) Know that science and medicine are ever changing, and
we learn more everyday (including sometimes, that we can be wrong). 3)
We do not have all the answers, and in fact we actually only know very
little. 4) Keep faith that as more is learned about the virus, better
treatments will come along, as well as better testing. 5) The more
doctors and scientists you ask, the more opinions you will get. Start
learning the science for yourself, and you may find you agree or
disagree with different treatments and proceedures. Try out those
treatments that you believe may work (do your homework first!!!). The
more informed you are, the better for your kitties.
I
have a feeling that alot of research will be done on FeLV and FIV.
Scientists are using it as a tool to learn more about HIV.
Hope
all is well.
Kate
__________________________________________________ Here is a list of articles and info to check out: www.vetscite.org/issue1/tools/leute_7_0800.htm www.healthgene.com/scripts/test.asp?code=D341 www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9026077&dopt=Abstract www.vet.ohio-state.edu/docs/vcs724/lectures/sherding/fiv.pdf www.marleyfund.com/testing.html www.vetmed.lsu.edu/oncology/RETRO.html www.laboklin.de/en/VetInfo/LABOKLIN%20aktuell/FeLV_FIV_FIP_questions.htm
(quote from:) FeLV-Diagnosis: http://www.users.waitrose.com/~thecatgroup/fiv.html Testing
for FIV There are
several test systems available for FIV including in-practice test kits.
In-practice tests detect anti-virus antibody, usually directed against
a viral
core protein (p24), the transmembrane
envelope protein
(gp40) or a combination of both. The most common test systems are based
on
enzyme-linked immunosorbent assays (ELISA)
or immunochromatography (IC). Combination
tests that enable
simultaneous testing for FIV and FeLV are
widely
used. The more specialised
tests include immunofluorescence and
western blotting
for the detection of antibodies to FIV, and virus isolation and
polymerase
chain reaction (PCR) for the detection of the virus itself. Several
laboratories use immunofluorescence as
their first-line
test, as this is very sensitive and detects antibody to any of the
viral
proteins. Western blotting is a second sensitive test, which allows the
detection of antibodies to individual viral proteins. Virus isolation
is
sensitive but is limited by practical considerations (expense,
facilities and
time) and it is not suitable for routine use. PCR tests, which detect
the FIV
nucleic acids (genetic material) are now more readily available and are
very
sensitive. Similar issues of
accuracy and the
potential for errors apply to the in-practice test kits for anti-FIV
antibody
as for FeLV antigen. Providing the test
has been
performed correctly with an appropriate sample, and the specificity of
the test
is very high, positive results are generally reliable. However, it is
recommended that a positive result on an in-practice test of a healthy
cat
should be confirmed by another type of test, such as immunofluorescence
or western blotting. The in-practice test kits require blood samples
and are
best performed with serum or plasma, rather than whole blood. As with
all test
kits there is a possibility for false positive and false negative
results. In
cats with a high suspicion of infection but which are negative on
in-practice
test kits, use of another test system to confirm the negative result is
also
highly recommended. www.vetscite.org/issue1/tools/txt_leut_0800.htm |
- RE: from Dr. Susan RE: PCR test and FeLV answer AnnLmla2
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- RE: from Dr. Susan RE: PCR test and FeLV answer AnnLmla2
- RE: from Dr. Susan RE: PCR test and FeLV answer AnnLmla2
- RE: from Dr. Susan RE: PCR test and FeLV answer AnnLmla2
- Re: from Dr. Susan RE: PCR test and FeLV answer anzajaguar