Article Notes
Early 2021 update of the 2020 Cochrane Review: Rapid, point-of-care antigen and molecular-based tests for diagnosis of SARS-CoV-2 infection.
Better data is now available on correlation between PCR cycle threshold and likely infectivity.
Although labelled as 'false' negative, negative RATs associated with positive PCR results, were in this study all in low viral-concentration patients, determined by a high PCR cycle threshold (ie. number of thermal cycles of RNA replication required before fluorescence is detected).
High PCR CT / calculated low-viral-concentration, correlates well with low/non-infectivity of the individual. This does not mean that they may not become infectious in the future, but rather means that at that point in time they are unlikely to be infectious.
Early 2020 studies of COVID rapid antigen tests were of low quality and of variable applicability to COVID diagnostic decisions. This situation improved dramatically in 2021 and 2022, and many RATs are now continually validated in existing and emerging variants.
This Cochrane Review was updated in 2021.