Tracking COVID-19 test results by the time of day that samples were collected from patients, the researchers report a 1.7-fold variation in the adjusted probability that a PCR (polymerase chain reaction) test would return a positive result: odds peaked at 2:06 p.m., when a positive result was 1.7 times more likely than at the daily low, shown in a graph to occur around 2 a.m. (the emergency room never sleeps).
