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August 22, 2020

AT HOME Covid-19 Test

Some scientists and epidemiologists believe that the pandemic would be even more rapidly controlled by a simple at home antigen test that could be used like a pregnancy test.  Nasal swabs or saliva must be added to a tube containing a liquid.  A paper strip coated with the virus antibody is then dropped into the liquid/test tube, and 15 minutes later the paper strip coated with a SARS-Cov-2 antibody will tell you if the virus protein antigen is present. 

In the one video I've seen, a positive control on the strip turns pink, and the adjacent strip also turns pink if the sample reacts with the antibody - meaning the virus is present in the sample.  The sensitivity is less than the molecular test, but the test becomes positive just about the same time as the virus replicates enough to be infectious and transmissible  (read more at rapidtest.com).  That makes it a very good test for "testing, tracking, and isolating,"

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       Example of positive test - paper strip in the tube.

The FDA doesn't yet have a way to evaluate these home tests - but the tests offer an easy, less expensive way to alert people who are infectious and should quarantine.  It is estimated that the paper strips could be very inexpensive ($1-2), meaning this test could be repeated every 1-2 days.   This test is a public health tool.  The current molecular Covid-19 tests are the gold standard, but are taking too long to complete, so they aren't as helpful for controlling the epidemic.

 

August 19, 2020

Point of Care Rapid Covid-19 Tests

It is hard to sort out the various tests available - but they still fall into two categories: molecular tests that amplify and then measure the virus nucleotides, and antigen tests that use a specific antibody to recognize the virus protein in the nasal sample.  Last Saturday the FDA gave Emergency Use Approval (EUA) to a Saliva Molecular Test developed by Yale and used by the NBA.  This would be lots easier, but it probably won't be widely available until they scale up production.

The Point of Care Rapid Tests (POC) are antigen tests, that must be done in Doctors Offices, Clinics, Nursing Homes, etc.  They require machines that have been developed by a company for a specific type of test, and employees must be trained to use the machines.  Antigen tests are not as sensitive as molecular tests.  They are most commonly positive when patients begin shedding virus, and turn negative within 10-14 days.  The molecular tests are positive earlier and remain positive later, even when there is dead virus in the nasopharyngeal swab sample.  Positive antigen tests should be confirmed with a molecular test if there are any questions about the diagnosis. A rapid point of care test can be done immediately, and a molecular test may take more than 4 days to a week to get a result.  The rapid tests mean that infected patients can be quarantined, their contacts traced, and isolated making it easier to control the pandemic.  Continue Reading.

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Next post I will describe a rapid at "home test" that is like a pregnancy test.  But this test needs a special FDA approval and the FDA will have to give emergency use approval as a public health tool instead of a highly sensitive and reproduceable molecular diagnostic test. 

August 15, 2020

Covid-19 Virus Testing - and Slow Results

Coronavirus testing can be done by PCR, a method to detect the genetic material of the virus, or by detecting the antigen of the virus.  The tests have different sensitivities, PCR can detect the virus when the viral load is too low to be easily passed on - or when it is detected at the end of the infection when only remnants of the virus are present.  The antigen tests are less sensitive and at the onset of the infection may be falsely negative.  But these tests can be done quickly, and in Nursing Homes, Medical Offices, and other places that have the machines and some training.

It is taking many days to get the results of the PCR test results almost everywhere, and this is unacceptable. if the tests are being done to quarantine infected people to prevent further spread, it is too late to have an impact on the infection rate.  The antigen tests are more rapid, but may need to be repeated and confirmed with a PCR test - depending on the circumstances.  Read more below.

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In order to get PCR tests back faster it is possible to pool samples from different people if the virus levels in the community are low.  NYC is testing 1000s of people every day and only 1% of the tests are positive.  If samples were pooled, here from 5 people for example, and the pooled sample tested negative, time and supplies could be saved.  If the pooled sample is positive, each sample would need to be tested.  But if the pool were larger and negative, even more time and supplies would be saved. Right now in states with a high percentage of positive tests, pooling wouldn't be feasible.  But if infected patients could be identified, isolated, and their contacts tested faster, we might be able to control the pandemic better. Is there a will to do this in our country?

Could we ever have at home tests, like a pregnancy test, that cost only $1-2, and could be done each day?  They were developed, tested, and can identify patients at the time they are infective.  But it is unclear where the funding would come from to scale up these tests. We can't even get our country to wear masks to decrease the number of infections.

Next time Point of Care Antigen Tests and Rapid At Home Tests. 

August 12, 2020

Can Schools Reopen Safely?

How many New York City Schools Will Reopen? 

New York City has < 1% positive Covid-19 tests each day, so the virus is being controlled.  And yet we worry about our students returning to school and getting infected.  There is not enough space for social distancing, and in older schools the ventilation may not be adequate. I volunteer in a school in the Bronx that was built in the late 1800s. 

Will there be an adequate number of teachers who are willing to return to the classroom, especially if they have underlying health risks or are in the vulnerable age groups?  This morning on NPR teachers were saying they really want to be with their students, but they have to feel safe.  Students and teachers will be required to wear masks all day, to remain socially distanced, and wash their hands frequently. 

Because of the lack of space, students will attend schools in smaller groups, perhaps 3 days one week, and 2 the next - and the other days will be virtual learning.  Earlier this summer 70% of schools did not have a full time nurse.  Many children in the public schools receive breakfast and lunch while at school.  They will eat their meals in their classrooms so students will not be in large groups in the cafeteria.  On the days when they are not in school, many students will need city-sponsored child care because they have  parents who are essential workers.  None of the plans are confirmed, and my grandchildren may not hear about the final plans until several days before school opens.  Read More Below.

 

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It would be wonderful if there were very cheap "at home" Covid-19 virus tests that could easily be done in the morning before students and teachers leave for school.  If positive, they would stay home.  There is good scientific data on these tests, and there is now a ground swell to get the FDA to give Emergency Use Approval (EUA) to them.  If approved, manufacturers can quickly make them available.   I hope to gather more information on these tests, which are similar to home pregnancy tests, later in this week.  Current tests that take many days to get results can't help us control the epidemic.

 

August 8, 2020

A Vaccine Challenge Trial?

Yesterday Richard Engel NBC National News, announced that scientists at Oxford's Jenner Institute in the UK are currently discussing a Challenge Trial of their Oxford AstraZeneca vaccine.  The vaccine is now in Phase 3 Clinical Trials in multiple countries.  There are many ethical arguments against a Challenge Trial in which all volunteers are vaccinated, and then several months later are given a measured, calculated dose of SARS-CoV-2 virus.  Oxford could enroll 40-60 volunteers and determine vaccine effectiveness in much less time. They say the Challenge Trial, which would be done in healthy 20 year olds, will have "minimal risks."  Vaccine Challenge Trials raise ethical questions, but were done previously for other pathogens. The problem in this instance, is the lack of effective treatment for those volunteers who do develop Covid-19?

Continue Reading Below: 

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Oxford AstraZeneca's standard Phase 3 randomized control trial is enrolling 30,000 volunteers - half will receive the vaccine and half will receive placebo.  No one including the patient will know what each volunteer receives until the end of the trial.  But if the volunteers aren't regularly exposed to the virus, it will take months to figure out the effectiveness of the vaccine.  Trial participants are told to lead their normal lives, but the trial will depend on them being exposed where virus infections are high.  The success of the vaccine is based on the number of cases of Covid-19 in the vaccinated group vs the placebo group.  In the US Moderna and Pfizer are also in Phase 3 testing with 30,000 volunteers.

  

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