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CDC has 2 strategies for d/c of home isolation/return to work-a test-based strategy, calling for 2 consecutive -PCRs >24h apart,+a non-test-based strategy, which permits return 72h s/p fevers have abated+respiratory improvement
I disagree strongly with both of these approaches.
I disagree strongly with both of these approaches.
The test-based strategy makes no sense. We know that patients will shed viral RNA for weeks following infection, and it has little relation to contagiousness/ability to infect others
See here
https://www.nejm.org/doi/full/10.1056/NEJMoa2002032
https://www.medrxiv.org/ …/10…/2020.03.09.20032896v1.full.pdf
See here
https://www.nejm.org/doi/full/10.1056/NEJMoa2002032
https://www.medrxiv.org/ …/10…/2020.03.09.20032896v1.full.pdf
The non-test-based strategy was developed based on data extrapolated from SARS and MERS (cited originally on this page, and later buttressed with COVID-specific publications: https://www.cdc.gov/ …/2019-ncov/hcp/disposition-in-home-pat…).
This was based off of observations that PCR threshold cycles > 33 correlated with low infectivity, and applying those findings to SARS-CoV-2.
You see, when we run a test for COVID, we place a sample into a machine and run a test called a polymerase chain reaction, or a PCR. It runs cycle after cycle until it can amplify the RNA of the virus to a level that is detectable by the machine.
So a "threshold cycle" is the number of cycles at which the amount of amplified genetic material crosses the threshold of detectability. The more cycles, the less viral genetic material was present at the beginning.
None of the SARS or MERS data can or should be applied to COVID. What little information we have (especially this NEJM LTE: https://www.nejm.org/doi/full/10.1056/NEJMc2001737…) fairly compellingly speaks against the SARS/MERS extrapolations.
What's more, my own experience has shown consistent PCR threshold cycles at multiple phases of illness, not reliably increasing at 72 hours post-symptom improvement.
I believe the CDC has fallen short multiple times in the COVID response, and the discontinuation of isolation/return to work guidance they've released continues a pattern of politics eclipsing science.
If you or a family member contracts COVID-19, consider delaying self-isolation until symptoms have abated for 7 days instead of 3.
You just might save a life.
You just might save a life.
