Why did the CDC change guidance on who to test? Read the Cohen-Kessel paper on false positive rate (FPR). They reviewed real-world data on RT-PCR tests for RNA viruses since 2004 & estimated 2.3% FPR. (1/6)
bioinvasions.org/wp-content/upl…
bioinvasions.org/wp-content/upl…
That means the specificity is 97.7%, not the fanciful 100% reported by labs (Table S1). Using 99% sensitivity & 97.7% specificity, then using the daily %+ tests to estimate the COVID-19 prevalence of the test population, it's possible to estimate... (2/6)
the number of + tests that were returned for uninfected people (i.e., false positives). Since 2/29, the US has 6.1M +tests, but 1.7M (28%) are likely false+. Also 45K of 77M (0.059%) false- tests (- test returned for infected people). (3/6) 
The problem is, as we increase testing and test more asymptomatic people, the chances of a false positive increases because the disease prevalence is decreasing. (4/6)
The last 30 days average 6.0% +tests so estimated prevalence and false+ average 3.8% and 38%, respectively. For the last 14 days, the numbers are 4.3%, 3.3%, and 42%... that's 222K people whose lives are suspended for 2 weeks for nothing. (5/6)
As early as 2/1, the WHO suspected the main driver of COVID-19 transmission was symptomatic cases. It's time to end the casedemic & focus testing on symptomatic people (or people likely to be infected) & reduce the number of false+ tests. (6/6)
who.int/docs/default-s…
who.int/docs/default-s…
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