It's not viremia ( Bloodborne ), as far as I have seen, so PCR testing of blood samples wouldn't show the presence, since it only takes a few viruses to travel through the blood to the kidneys, and a moderately high viral load is required in a sample for PCR to be effective

2019-nCov is not bloodborne, ( Infecting blood cells ), but exploits the circulatory system, obviously, because the first place viruses are going to end up after an infected cell finally bursts in the lungs is in the nephron tubules of the kidneys ( The waste handlers )