Direct HIV testing is not only in practice, but it is also being
'taught' to college level students involved in virology. A studyguide
for the 400 level course midterm reads (link below). I've listed only
part of the answer to comply with copyright of the original page,
please click on the link for the full explanation of direct HIV
testing.
"Question: You are given a blood sample of a patient who may have been
exposed to human immunodeficiency virus (HIV). What would be an
appropriate way to test whether or not this patient has indeed been
exposed? Describe the steps involved in your approach.
It would also be possible to test for HIV directly in the patient's
blood cells using some method to detect HIV-specific nucleic acid
sequences. For example, you might look for HIV- specific mRNA by
Northern blot, or for HIV-specific DNA by Southern blot or the
polymerase chain reaction."
Also, Dr. Patrick Dixon discusses in his 1994 book entitled, "The
Truth About AIDS" states:
"It is possible to test for HIV directly, not waiting for antibodies
to develop. This method looks for viral genes---the DNA instructions
that the virus inserts into white cells to hijack them into virus
factories.
A special chemical reaction is used called PCR (polymerase chain
reaction), which can multiply a million copies of viral DNA in three
hours, and combined with other equipment can detect as little as one
piece of viral DNA in ten microlitres of blood. The test has been
useful in some situations to detect possible infection far earlier
than antibody tests. More than 90% of antibody positive people also
test positive by PCR, but not all. The technique is extremely
sensitive to cross-contamination from previous samples. It is very
easy to get false positive results.
Viral culture is another method of testing, where attempts are made to
obtain HIV from white cells. It can detect 50% of HIV-infected
children at birth, unlike antibody testing.
In conclusion then, HIV testing is now very accurate indeed, although
the initial test result always needs to be confirmed."
Please remember that these two procedures were experimental at the
time of his book (1994) and have had 8 years to be developed, refined,
and eventually made common place enouhg that it is taught in college
level courses. So the question you may ask next is, "Why isn't
HIV-direct testing more prevalent?" The answer to that question is
money. These tests are very difficult to run, and are multi-step as
described briefly on the two pages above. It is not economically or
logistically feasible to offer this test as a first option, although
I'm sure some labs would run this test if requested by a
hospital/clinic.
Additional Links
Virology 442 course midterm study guide at University of Waterloo:
http://www.science.uwaterloo.ca/course_notes/biology/biol442/answ4.html
Link to excerpt from Dr. Patrick Dixon's book (copy and paste URL into
browser or you'll have to click manually on "How accurate is testing
for HIV":
http://www.globalchange.com/ttaa/ttaa%205.htm#Q.´How accurate is
testing for HIV?
Search Strategy:
"test for HIV directly" on google:
://www.google.com/search?q=%22test+for+HIV+directly%22
Thank you for the opportunity to answer your question, if you require
more information, please clarify the question, or if you find this
answer satisfactory, please feel free to rate it. Thank you!
skermit-ga |
