COVID-19 Testing: Miami Doctors Explain Best Practices for At-Home, PCR Tests

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A surge in COVID-19 cases driven by the omicron variant has pushed testing capabilities in South Florida and across the country to the limit.

There are long lines for PCR tests at free county-run sites and at-home antigen tests are out of stock at most stores.

If you have symptoms such as a sore throat, congestion or fever doctors recommend you isolate until you can get a test. Even then, however, one test may not be enough.

NBC 6 reporter Laura Rodriguez tested positive with an at-home test and the following day she went to get a PCR. The PCR test, considered the gold standard, came back negative. Rodriguez followed up with another PCR test and that one came back positive.

"Symptomatic antigen is great for detecting the virus within a few days of infection. PCR tests can fluctuate up and down so if you have a viral load that is near the limit of detection for testing it can fluctuate between positive and negative,” said Dr. Jillian Harrington, Nomi Health Laboratory Director.

Dr. Harrington says it is also possible the swab was done incorrectly.

"Testing is only a moment in time, it doesn't tell the whole story, it's not the whole movie and that’s why these different pictures and these serial tests, the serial home rapid testing, really improves the sensitivity,” said Dr. Geeta Nayyar, University of Miami Associate Professor of Medicine.

Dr. Michael Mina, Chief Science Officer for Miami-based company eMed, suggests having a strategy for using the few at-home rapid tests currently available.  

"What we have to do now if we want to use these in a smart way is to use them with strategy. There are a number of different places where we can use them. If you are positive, use it to get out of isolation early. That’s a good use of a rapid test. If you know that you've been exposed and you become symptomatic, don't use the test right away, give your body another day. But assume that you are positive and revisit on day 2 or 3,” said Dr. Michael Mina, former assistant professor of epidemiology and immunology and infectious diseases at Harvard T.H. Chan School of Public Health.

Mina, an immunologist and epidemiologist, believes COVID testing needs to be fast, frequent, and accessible. He is a major proponent of rapid antigen tests and believes the United States has not made rapid testing a priority, leading to what he calls a failure to the COVID-19 response.

"I'm not surprised about any of this. I was writing about what we are seeing today a year and a half ago. It is not surprising for people who understand the dynamics of infectious disease pandemics and who also understand the testing infrastructure. We had to start scaling up our tests months ago to be able to deal with omicron today,” said Dr. Mina.

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