The technical details of COVID-19 testing aren’t something most of us are familiar with, if you don’t know what a PCR molecular test is, join the club, I didn’t either, but it turns out the way the testing is being done may result in far too many positive results.
How it works – a quick description
A sample is gathered from someone and sent to a lab. The sample is heated and cooled a number of times to amplify any virus that might be present. This cycle is repeated and the number of times necessary to find any virus is called the cycle threshold, fewer cycles means more virus and it’s more likely that person is contagious.
What’s the problem?
The test result is given as either positive or negative, but the cycle threshold isn’t mentioned so a person who is highly contagious with a lot of the virus and someone with a tiny amount and not contagious and unlikely to get sick, are both reported as positive cases. Instead of quickly finding the cases we’re looking for and isolating and treating those individuals, the tests keep running over and over to find what isn’t necessary.
In three sets of testing data that include cycle thresholds, compiled by officials in Massachusetts, New York and Nevada, up to 90 percent of people testing positive carried barely any virus
On Thursday, the United States recorded 45,604 new coronavirus cases, according to a database maintained by The Times. If the rates of contagiousness in Massachusetts and New York were to apply nationwide, then perhaps only 4,500 of those people may actually need to isolate and submit to contact tracing.
One solution would be to adjust the cycle threshold used now to decide that a patient is infected. Most tests set the limit at 40, a few at 37. This means that you are positive for the coronavirus if the test process required up to 40 cycles, or 37, to detect the virus.
Tests with thresholds so high may detect not just live virus but also genetic fragments, leftovers from infection that pose no particular risk — akin to finding a hair in a room long after a person has left, Dr. Mina said.
Rapid tests may help
Rapid tests are not as sensitive as the PCR test, but can deliver results in as little as 15 minutes and will find those who are highly contagious. These are a big step in the right direction.
What does this mean?
As noted above, positive case numbers could be as much as 90 percent too high, the real totals may be a fraction of what news reports and government officials are telling us. Combined with the previous article here showing that COVID-19 rarely acts alone, but is often an additional cause of death, not the sole cause, it now appears the presentation of the danger of COVID-19 may be, well, … wildly exaggerated.
Is it? You decide.
Via a very informative article from the New York Times