Key words: COVID-19, SARS-CoV-2, Rapid Antigen Tests, rRT-PCR
Abstract
The most widely used test for the diagnosis of SARS-CoV-2 infection is a PCR test, which has
very high sensitivity and is able to detect very low amounts of RNA. However, many individuals
receiving a positive test result in a context of a PCR-based surveillance might be infected with
SARS-CoV-2, but they are not contagious at the time of the test. The question arises regards
if the cost effective, portable rapid antigen tests (RATs) have a better performance than PCR
in identification of infectious individuals, as well as their homogeneity of performance. In this
direction, we examined the diagnostic performance of RATs from 14 different manufacturers
in 400 clinical samples with known rRT-PCR cycles threshold (cT) and 50 control samples. The
intensity of bands of the RATs was assessed by colorimetric quantification. The intensities of
the bands perfectly correlated with rRT-PCRs cTs (p<0.0001). However, substantial variability
was observed in the limit of detection (LOD) of different RATs (cT=26.8-34.7). The overall LOD
for all 14 RATs tested was cT=31.1 and for the 5 most sensitive RATs it was cT=33.7. Especially,
for the fluorescence-based RAT the LOD was cT=34.7. The use of the 5 most effective RATs
leads to an augmentation of the acceptable true positive rates of 88.2% and 80.0% (for
samples with cT<=30 and cT<=33) to 99.1% and 90.9%, respectively, percentages that can
guarantee a sensitivity high enough to identify virus transmitters. RAT testing may also
substantially reduce the quarantine period for infected individuals without compromising
personal or public safety.
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