Ah, this may explain a lot...
https://www.mayoclinic.org/covid-antibody-tests/expert-answers/faq-20484429
FWIW, I think the prez deserves better than quicker and cheaper. If someone is getting near him, use the better test.
But “the better test” takes very much longer.
He can’t wait for that.
The quicker test is faulted for missing less infectious people.
“Infectiousness” is what we want to keep from Trump.
Not perfect, I admit.