Diagnostic performance of Rapid Antigen Tests for SARS-Cov-2. Are RATs more useful than PCR tests?

Key words: COVID-19, SARS-CoV-2, Rapid Antigen Tests, rRT-PCR


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.

Full article below:

Diagnostic performance of Rapid Antigen Tests (RATs) for SARS-Cov-2
. Are RATs more useful

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