07 February, 2024
Q: Does a negative rapid antigen test rule out infection or mean a patient cannot be contagious?
A: If a person has symptoms or suspects they have infection, a negative antigen test does not rule out the possibility they could be infected and contagious. The test may have been taken at a point when not enough virus was present to reach the limit of detection or be due to sampling error. In general, antigen tests turn positive ~1 day later than PCR tests but turn negative faster after infection has resolved, reflecting the fact that it takes more virus present for a rapid test to turn positive. There is a positive correlation between a true positive antigen test and contagiousness, but the relationship is complex. The likelihood a person transmits to another person depends not only on the amount of live virus but also its inherent transmissibility, the amount of exposure time, ventilation, the use of masks and vaccination status.READ MORE