04/06/2020
Sharing this post from Dr. Edsel Maurice Salvana: :-)
Food for thought and why RT PCR testing should be exposure-based and properly timed. Another reminder on why doctors should be determining who to test. Even RT-PCR can have a false negative if testing is done too early or too late:
"Over the 4 days of infection before the typical time of symptom onset (day 5), the probability of a false-negative result in an infected person decreased from 100% (95% confidence interval [CI], 100%-100%) on day 1 to 67% (CI, 27%-94%) on day 4. On the day of symptom onset, the median false-negative rate was 38% (CI, 18%-65%). This decreased to 20% (CI, 12%-30%) on day 8 (3 days after symptom onset) then began to increase again, from 21% (CI, 13%-31%) on day 9 to 66% (CI, 54%-77%) on day 21. The false-negative rate was minimized 8 days after exposure—that is, 3 days after the onset of symptoms on average."
In other words, even if you ARE infected with COVID-19, the probability that your RT-PCR will be POSITIVE (even if you are infected) is:
Day 1 of exposure: 0%
Day 5 of exposure, 1st day of symptoms: 62%
Day 8 of exposure, 3rd day of symptoms: 80%
Day 21 of exposure, likely no more symptoms: 34%
There is NO utility to testing asymptomatic persons who just got exposed. We need to quarantine them for about 5 days before considering testing. Best time to test is 8 days post-exposure. Testing asymptomatic people without exposure to COVID-19 using RT-PCR is not advisable because of a high false negative rate without proper timing. Let's use our limited resources wisely and understand the limitations of the tests.
Background: Tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) based on reverse transcriptase polymerase chain reaction (RT-PCR) are being used to “rule out” infection among hig...
