Quoted from Healthline: "The RT-PCR nasopharyngeal tests are more widely used and more familiar. Most involve sticking a 6-inch swab deep into your nose to collect virus samples to test.
However, some more recently approved RT-PCR tests seek to avoid the discomfort associated with the nasopharyngeal swab tests by allowing samples to be collected via a shallow swab of the nose or by testing saliva for the presence of the virus.
If performed correctly, RT-PCR swab tests “would be pretty close to 100 percent accurate,” Volk told Healthline.
“We should be diagnosing people with PCR tests because they are the most accurate,” added Dr. Christina Wojewoda, a pathologist at the University of Vermont and vice chair of CAP’s microbiology committee.
(I think the 2 week quarantine is to allow symptoms to emerge or the covid to build up to measurable swabs.
My hypothesis anyways.)