Have you been to this website yet?
Today, the White House officially launched
a site where you can order free at home
COVID tests that will be delivered
right to your door. The addresses
covidtests.gov, but how accurate
or reliable are these tests joining
me now is Doctor Jeffrey Baird.
He's the chair of UW Medicine's Department
of Laboratory medicine and pathology.
Dr Baird good morning to you.
Good morning to you too.
So these rapid tests are pretty exciting
because they make testing really easy
and convenient to do right at home.
But we've heard that people have had
false negatives with these antigen
tests where they test negative first
with the antigen test and then they
later test positive with a PCR.
Can you tell us more about the accuracy
and reliability about these tests?
Yeah, the the unfortunate thing that
we're dealing with right now is the
speed of the Omicron wave coming
through where we don't have as much
data as we have on other variants,
but throughout the history,
since we've had the engine test,
they've in the symptomatic people,
so if you have a fever or chills
or cough something like that,
they're around 90% as as sensitive at
picking up the disease as a PCR test.
The real problem is with the asymptomatic
individuals or screening before going to
something where they really don't have
the sensitivity that a PCR test does.
So the best use for these things is
going to be if you're feeling down
or if you feel sick to use it there.
When is it a good idea to then maybe
say if you got a negative antigen
test and you do have symptoms,
do you recommend then go and seek
out a PCR test just to make sure?
So, so that that changes
depending on the time.
Right now the prevalence of the
disease is so high in the population
we're seeing over 10% in just,
you know, random samples pretty
much of of folks and earlier in.
In other countries there have been,
you know, times when the the
carriage rate has gotten over 25%.
At that point,
positives are probably real positives,
and you probably don't
need to get a second test.
However, after the surge is over here
in a in a in a few weeks, it once.
Once things are not so common.
You may want to then,
if you really don't think
that it makes much sense that
you haven't been exposed,
you might want to confirm with the PCR test,
but for right now,
if you're feeling ill and you do do
an antigen test and it's positive,
you should consider that to be a positive.
We're learning a real positive, OK,
good to know, and we're learning
a lot about this Omicron variant,
and information is coming
in by the day about it.
What do we know about when people
are infectious and how these
antigen tests come into play
about when people get tested?
So we have known for quite some time
that you're most infectious in the
few days following a infection and
then just before you feel symptoms
and then in the first couple days.
That's when usually it's the most when
you have the most symptoms and you
also have the most virus in your body,
meaning that it's easiest to
detect with the antigen test.
The thing that we're noticing
with the Omicron variant, though,
is that there have just been
some very small reports really,
just two pre printed papers,
not yet peer reviewed,
and a lot of tweets honestly.
But they're they're saying that,
yeah, it may just be that antigen
tests are negative for another day or
two longer than we would expect for,
say, the Delta variant.
So there might be a little window there
where you might not have symptoms.
You would test negative,
but you might still be infectious,
which is why right now,
with such high prevalence is,
it's probably not the best thing to
do to still have those gatherings
and rely on the test.
The test really can't be relied
on right now for that purpose.
OK, as antigen?
Lastly,
when you get these tests.
In the mail and you use them.
What's the best thing for people
to know and understand when
they're using the test at home?
The important thing is to follow
the instructions as carefully
as you can believe it or not.
Those little plastic devices,
those are precision made medical devices
and it's really important that you
follow all of the instructions on them.
And when it says to look at it
after a certain number of minutes,
you know user watch,
user stopwatch or use your watch
and look at that and make sure that
you read it at the right time so
you actually get the best possible
result that you can out of it.
Great
information. Doctor Jeffrey
Baird with UW medicine.
Thanks so much for joining us.
Once again thank you.