NEW: Did you know that the PCR test offers a rough approximation of the viral load and not just a yes/no to the question of infection? So why do labs not report it? Dozens of studies have shown that the viral load can predict outcome, including death 1/7 https://www.nytimes.com/2020/12/29/health/coronavirus-viral-load.html

Baked into the PCR is a metric called Ct, or cycle threshold-- the number of cycles the PCR has to run to get a positive signal. The more virus a person has, the lower the Ct--and, apparently, the greater the odds of severe illness and death, according to these studies 2/7

So why do labs not report Ct values? Every lab scientist I've spoken with has been under the impression that the FDA's authorization of the tests only extends to a yes/no, but in fact, acc to the FDA, that is NOT SO, and this month the FDA updated its FAQ to reflect this 3/7

Labs can absolutely reveal Ct values to doctors and patients. There are huge caveats: Ct values vary between machines, and even in the same machine depending on who is handling the samples and how. 4/7

More importantly, Ct values vary over the illness--from high at first to low and then a long tail of high values, even long after the live virus is gone. But ultimately, a low Ct would still signal that a patient needs careful monitoring, several scientists told me. 5/7

Providing Ct values might also show that a person who tests "positive" for weeks afterward is shedding just viral fragments and isn't a real threat to anyone -- solving an issue I brought up in this article in August 6/7 https://twitter.com/apoorva_nyc/status/1299705092178956288?lang=en

There are as many opinions on this topic as there are scientists, but I tried to sample enough of them to get at common ground. Many thanks to:
@DanielGriffinMD @michaelmina_lab @GreningerLab @jameshay218 @celinegounder @SBtotheDub and Michael Satlin https://www.nytimes.com/2020/12/29/health/coronavirus-viral-load.html