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03.08 - Update on Testing
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來自 University of Michigan 的課程
AIDS：恐惧与希望
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從本節課中
Unit 3 - Testing (and Some Politics and Memories)
The Critical Issue--Testing
與講師見面
Richard Meisler, Ph.D.Lecturer
Department of American Culture, University of Michigan
Doctor James Riddle is an infectious disease specialist in the University of
Michigan health system.
He is one of the resource people I go to frequently to learn about the science and
medicine of HIV and
he is also kind enough to be a guest speaker in my on campus class.
We will see a lot of Dr. Riddle in future sessions but today, I want to share with
you a short segment of a conversation that I had with him concerning HIV testing.
Dr. Riddle mentions two terms that you will hear frequently in
discussions of HIV testing, ELISA and Western Blot.
Both are tests for antibodies against HIV.
The ELISA test is the first test generally done to detect antibodies to HIV and
it is an acronym for Enzyme-Linked Immunosorbent Assay.
The Western Blot is a more detailed test to confirm a positive ELISA test.
The main point is that we don't test directly for HIV in the blood or
other bodily fluids.
Antibodies are one of the immune systems tools to fight infectious.
They are proteins that are much easier to test for than the virus itself.
One of the problems of antibody testing is that there is a window period.
A period between the time that a person is infected and
the time that antibodies develop and are detectable.
In this session, recorded in the summer of 2014, Dr.
Riddle describes new developments that reduce this window period from
weeks to days, a big step forward.
Here's a segment of that conversation with Dr. Riddle.
Just before we started to record,
you surprised me with some brand new news about testing.
Why don't you tell us where we stand with, recommendations for testing,
and what's just changed.
>> Sure.
So the previous way HIV testing was performed was with an ELISA test,
it detected HIV1 and HIV2 antibodies.
If that test was positive, it's a colorimetric test, so
basically if it turns a certain color, that would be considered positive, and
then the sample would be refered on for what's called western blot testing,
where they look for anti-bodies against certain HIV capsize entities.
Now, the problem with that approach is that anti-bodies
detected in the western block take time to evolve.
So, there can be a window period of a period a week
to two weeks where those bands may be absent.
It maybe therefore difficult to confirm the presence of HIV,
and >> So, I may just of been, I may of just
been infected, I'm scared, I go in for a test but it's within that window period.
And I have been infected, but the antibody tests won't come up as positive.
>> Exactly. So
that initial antibody test may be negative because we have not generated those
antibodies or the western blot may be negative or what we call indeterminate.
Meaning there's only a couple of bands present.
So, the newer recommendations now to try to pick up those patients who are in those
very early stages of infection are to use an initial combination task that uses
HIV 1 and 2 antibody detection, in to what's called a P24 antigen detection.
And P24 antigen is a antigen that's
present on the surface of the HIV capsid itself.
And can be detected in blood.
And by using that combination, hopefully we'll be able to detect people
at an earlier stage of infection, not miss those people who are in the window period.
>> Is it gonna shorten the window period, or eliminate it?
>> Well, virtually impossible to completely eliminate,
[LAUGH] the window period because there is a time at which
you become infected with HIV and it's not even detectable in your bloodstream
which has been called by some the eclipse period.
[LAUGH] >> Uh-huh.
>> And there have been some outbreaks
linked to eclipse period where it's been missed.
So it's not going to be possible to detect
it in everybody, but hopefully earlier. >> Is the eclipse period a day or
two? >> WIthin sort of a three to five day
period before it's detectable in the blood.
That's right.
>> So, it reduces it from weeks to days.
>> That's right,
which can still be important because there are still
a significant number of patients who are in that period.
>> The CDC, of course, has also, over the last few years,
changed its recommendations to try to >> Encourage healthcare
providers basically to test everyone >> That's right.
>> To have universal testing.
How's that going?
>> Yeah, I haven't seen statistics on exactly what
the uptake of that's been like, but
I can just tell you, in our system, >> And
we've been able to have HIV testing in our emergency department now for
what, for several years which didn't previous exist, rapid testing there.
It's more widely available and easier to administer in the outpatient clinics.
Because of some of the restrictions that have been lifted for
the way informed consent is provided
making basically informed consent easier to provide to the patient.
>> Out patients at this point are asked to opt out, rather than opt in.
Is that correct?
>> In some ways, or if you're going to perform an HIV test,
you can verbally just tell the patient about the test.
>> Don't need an elaborate document.
>> As opposed to an elaborate document that you have to search for and fill out,
which has been limiting.
Quite honestly in the past.
I think it's much easier to have for that whole process to occur.
So we're probably making progress with that locally.
>> I think so. >> Do you have any idea how we're doing
nationally?
>> Yeah, the national level not sure.
I haven't seen statistics exactly on how many more tests are being done now than
there used to be.
But that would definitely be something interesting to just to find out about.
