Coronavirus Epidemic Update 27: Testing accuracy for COVID-19 (CT Scan vs. RT-PCR), California Cases


welcome to another MedCram update let’s
talk about California and testing but before we do let’s just review total
confirm eighty 2164 total deaths 2800 oh one total recovered thirty two thousand
eight hundred and ninety seven we see more of a continuation of what we’ve
been seeing in the past let’s go to the world ometer we gonna talk a little bit
about testing today and also the positivity rate and UK they have well
over seven thousand tests of which only thirteen are positive and that’s a very
low positivity rate of course in Italy where they actually have an outbreak
they’ve done over nine thousand tests of which only four hundred and seventy are
positive it’s about a five percent positivity rate in France two point two
positivity rate in Austria 321 tests of which two are positive and then in the
United States notice we’ve only done four hundred and forty five concluded
tests of which fourteen are positive and that’s around three point one positivity
rate these tests are not as sensitive as you may think that you’re going to be
surprised that the sensitivity on these tests are only around seventy percent
and so it is possible to have a negative test and to still be infected with the
corona virus we see that there are so far 334 new cases and one death in South
Korea and the number of confirmed cases expected to jump in the coming days as
health authorities have started testing more than two hundred and ten thousand
members of this church and Daegu if we look at the numbers coming out of China
and the rest of the world in terms of the total deaths that seems to be
leveling off and if we look at the number of daily new cases outside of
China that has hit its highest amounts ever on February 26 with daily cases of
569 I want to go to a local site Eyewitness News
here in Southern California a new case that has been detected in Northern
California in a resident who has not traveled overseas
couple things that I want you to be aware of this patient is a resident of
Solano County turns out that Solano County is the home to Travis Air Force
Base where Americans returning from overseas were quarantined the patient
was transferred back on February 19th so that was about a week ago from
undisclosed hospital to UC Davis health and that is the hospital in Sacramento
for the University of California Davis patient had already been intubated was
on a ventilator and was given droplet precautions orders because of an
undiagnosed and suspected viral condition so there are other viruses
that can do this now at the time it seems as though UC Davis had asked the
CDC for testing but this was not done at the time and if you go to the CDC
website it tells you what their requirements are for testing although
they do put a disclaimer that they will look at a case-by-case basis but
essentially unless you traveled to Wuhan or that part of China they weren’t
really going to be doing that kind of testing so it’s unclear how eventually
UC Davis was able to get CDC to test this patient but they did and eventually
on Sunday the CDC ordered the Cova 19 testing of the patient at that time the
patient was put into airborne precautions what does this mean it means
that anybody going into that room had to have an n95 mask and had to go into
contact isolation precautions that means they would have to wear a gown gloves
they may even have to wear I wear protection if they were not able to do
that then they would have to go under something called poppers where they
basically go in with a mask that was vented from Sunday to Wednesday it took
for the CDC to confirm finally that the patient’s test was positive the small
number of employees were to go home and monitor their temperature for any kind
of fever or things of that nature and the key here is to recognize
apparently this patient had no travel to that part of the world they go on to say
here at this time the patient’s exposure is unknown it’s possible that this could
be an instance of they call community spread of kovat 19
which would be the first time that this has happened in United States
it’s also possible however they said that the patient may have been exposed
to a returned traveler who was infected of course this brings up the issue of
anybody that comes when with fever or signs and symptoms of a viral illness
and shortness of breath could be potentially a carrier of this novel
coronavirus and that’s why it’s really important to have lots of personal
protective equipment at hospitals where they belong instead of running out at
hospital so it’s really important that hospitals have the ability to acquire
personal protective equipment because you don’t want to show up to a hospital
where the employees there or the doctors or the nurses don’t have the adequate
amount of protection so that they don’t pass the virus on to anybody else that
might show up at that hospital so please do not take masks and protective
equipment from hospitals for your own use but this really brings up a big
issue and that is how do you test people for coronavirus how do you know quickly
whether or not this person that’s coming in has this virus obviously if we see
here in this case it took them from Wednesday when they actually got the
causative test all the way from Sunday when they first order the tests you can
see that that’s not the optimal situation especially when we add to the
situation that this test is not really that sensitive meaning that if you have
a negative test you can absolutely rule it out so enter a study that I think is
going to be important and that is this science Daily News article which talks
about this article that was just published in radiology called CT
provides the best diagnosis for kovat 19:00 I will put a link to it in the
description below basically what they did is in China they looked at over a
thousand patients and they did this reverse transcriptase polymerase chain
reaction which is what rt-pcr stands for this is where you look for the actual
RNA of the patients and compared it to the classical findings that they see on
CT scan here’s another news item of the same article so title as CT provides
best diagnosis for kovat 19 and it says the study from China shows that chest CT
demonstrates better sensitivity than this blood test looking for the actual
pcr of the virus remember that halfway through the
epidemic last month they changed the criteria in the definition for the
diagnosis of kovat 19 so you can see here in a study of more than a thousand
patients that was published in the journal article radiology which we link
to so you can look at it for yourself chest CT actually outperformed lab
testing in the diagnosis of 2019 novel coronavirus and this was looked at in
Wuhan China so it’s important to understand that you have to make an
early diagnosis of kovat 19 if you’re going to isolate and you’re going to
prevent the spread of that disease as we talked about earlier in a early jam
article 41 percent of patients who contracted Co vyd 19 did so in the
hospital and the majority of those 41 percent were healthcare workers
according to the latest guidelines by the Chinese government the diagnosis
must be confirmed by reverse transcriptase polymerase chain reaction
or the gene sequencing they say here however that those throat samples are
only about 30 to 60 percent positive at initial presentation having a low
sensitivity implies that there’s going to be a lot of people who will be
negative initially and you’re gonna miss those people those people are going to
come through into your hospital and potentially infect other people
specifically people who are there to help and causing them to be taken out of
work and put into isolation most likely and so they say here that early
diagnosis of copán 19 is crucial for the disease treatment and control compared
to rt-pcr that is the genetic testing they say here that chest CT imaging may
be a more reliable practical and rapid method to diagnose and assess kovat 19
especially in the epidemic area so why did they think that well let’s take a
look and see this there was over a thousand patients who
underwent both CT chest and rt-pcr tests from January 6 to February 6 and what
they did was they looked at all of those people who had a positive PCR and there
was about six hundred and one of those and everybody that had a positive CT
scan and there was eight hundred and eighty eight of those and then they
asked the question well what’s the sensitivity what’s the specificity and
what’s the accuracy and what they found was that about eighty one percent of
patients with a negative rt-pcr but a positive CT scan were reclassified
as highly likely or probable cases with kovat 19 based on the comprehensive
analysis of clinical symptoms typical CT manifestations and dynamic CT follow-ups
what they mean by that they were getting worse and they were consistent they also
found in a lot of these that the initial tests may have been negative but that
follow-up tests turned positive confirming in a lot of these cases the
original CT findings let’s review those results the results showed that 59
percent of these patients that they tested had PCR results that were
positive eighty eight percent had positive CT scans they said that the
sensitivity and this is something that you want to be very very high in this
situation because something that is very sensitive means that if it is negative
you can practically rule it out and as it turned out that sensitivity of chest
CT was 97% based on positive rt-pcr results in patients with negative rt-pcr
results seventy-five percent of those patients had positive CT findings and of
those forty eight percent were highly likely cases so what we’re seeing here
is that CT scans may be the way to get a quick screening of whether or not your
patient with fever is likely to have kovat 19:00 but the question is what are
the findings on CT it’s good enough to know that you should get a CT but what
is it that you should be looking for I’m going to link in the description below
a youtube video describes the findings on CT scan of known cases of copán night
and that concludes our update for today realize that many of these videos are
made the evening before they get released because I still am working in
the intensive care unit seeing patients every single day and so this is
something that I do at the end of the day because we as healthcare providers
are on the front line and we have to be prepared thanks for joining us