The NFL has been using an unproven measure to get players with Covid back on the field fast, Salon.
Interesting article which highlights the lack of a diagnostic test that is able to give a timely indication that an infected player has ceased to be infectious. PCR tests will report infection even after the player ceases to be infectious. That will no doubt be an issue the AFL has to tackle too and it might adopt the NFL's policy as more players will be available to play under it.
To determine whether a player remained infectious, the NFL adopted a threshold of 2 negative PCR tests or 2 "faintly positive" PCR tests or 1 of each. They defined "faintly positive" as having a cycle threshold (or Ct value) of 35 or higher. The Ct value reports "how many times the [PCR] machine had to copy the genetic material of the virus in the sample before it yielded enough to actually see". A high Ct value suggests there's so little genetic material in the sample that the PCR machine needed to copy it over and over until there was enough to detect. That would suggest the person who provided the sample didn't have enough Covid to be infectious.
But that test remains controversial as it isn't a standardised measure and is affected by how the sample is taken; e.g. did the patient cough before the sample was taken or did the person who took the sample hit the right spots.
It seems it's halfway between solid science and witchcraft but it may well be a good halfway solution.
Interesting article which highlights the lack of a diagnostic test that is able to give a timely indication that an infected player has ceased to be infectious. PCR tests will report infection even after the player ceases to be infectious. That will no doubt be an issue the AFL has to tackle too and it might adopt the NFL's policy as more players will be available to play under it.
To determine whether a player remained infectious, the NFL adopted a threshold of 2 negative PCR tests or 2 "faintly positive" PCR tests or 1 of each. They defined "faintly positive" as having a cycle threshold (or Ct value) of 35 or higher. The Ct value reports "how many times the [PCR] machine had to copy the genetic material of the virus in the sample before it yielded enough to actually see". A high Ct value suggests there's so little genetic material in the sample that the PCR machine needed to copy it over and over until there was enough to detect. That would suggest the person who provided the sample didn't have enough Covid to be infectious.
But that test remains controversial as it isn't a standardised measure and is affected by how the sample is taken; e.g. did the patient cough before the sample was taken or did the person who took the sample hit the right spots.
It seems it's halfway between solid science and witchcraft but it may well be a good halfway solution.