Diagnostic Performance of Rapid Antigen Testing for SARS-CoV-2: The COVid-19 AntiGen (COVAG) Extension study

Publication date: Nov 28, 2023

Background: Rapid antigen tests (RATs) for SARS-CoV-2 have been used to combat the still ongoing Covid-19 pandemic. This study is the extension of the COVAG study originally performed from February 1 to March 31, 2021. We compared two RATs, the Panbio COVID-19 Ag Rapid Test (Abbott) and the SD Biosensor Q SARS-CoV-2 Rapid Antigen Test (Roche), against RT-PCR on the foil of new variants. Methods: We included 888 all-comers at a diagnostic center between October 20, 2021, and March 18, 2022. RT-PCR-positive samples with a Ct value [≤] 32 were examined for SARS-CoV-2 variants. Findings: The sensitivity of the Abbott-RAT and Roche-RAT were 65% and 67%, respectively. For both RATs, lower Ct values were significantly correlated with higher sensitivity. For samples with Ct values [≤] 25, the sensitivities of the Roche-RAT and of the Abbott-RAT were 96% and 95%, for Ct values 25-30 both were 19%, and for Ct values [≥] 30 they were 6% and 2%, respectively. The RATs had substantially higher sensitivities in symptomatic than asymptomatic participants (76, 77%, vs. 29, 31%, for Abbott-RAT, Roche-RAT, respectively) and in participants referred to testing by their primary care physician (84%, 85%) compared to participants who sought testing due to referral by the health department (55%, 58%) or a warning by the Corona-Warn-App (49%, 49%). In persons with self-reported previous Covid-19 sensitivities were markedly lower than in patients without previous Covid-19: 27% vs. 75% for Roche-RAT and 27% vs. 73% for Abbott-RAT. Depending on the vaccination status, the sensitivity of the RATs is 67.6%, 61.5% and 70.6% for non-vaccinated, vaccinated and boostered participants, respectively. For the considered subpopulation of 888 participants, we find no significant correlation between vaccination status and sensitivity. The Omicron variant was detected with a sensitivity of 94% and 92%, the delta variant with a sensitivity of 80% and 80% for Abbott-RAT and Roche-RAT, respectively. This difference is attributable to the lower Ct values of the Omicron samples compared to the Delta samples. When adjusted for the Ct value, a multivariate logistic regression did not show a significant difference between Omicron and Delta. In terms of sensitivity, we found no significant difference between the wild-type and the Omicron and Delta variants, but a significantly lower sensitivity to the alpha variant compared to the other variants. For a Ct value [≤] 25 the sensitivities were 95.2% and 96.0% for the Abbott-RAT and the Roche-RAT, respectively (Table 4). For a Ct value of 25-30 both RATs had a sensitivity of 18.8%. For a Ct value of 30-32, the sensitivities were 0.0% and 7.1% respectively, for Ct values [≥]32 the sensitivities were 3.0% and 6.0% for Abbott-RAT and Roche-RAT, respectively. The specificities were >99% overall. Interpretation: The sensitivity of the RATs for asymptomatic carriers is unsatisfactory questioning their use for screening. When used in symptomatic patients or when requested by a primary care physician the sensitivities were higher. Our study does not suggest that the vaccination status influences the sensitivity of RATs.

Concepts Keywords
Austria Abbott
Pandemic Cov
Pcr Covag
Vaccination Covid


Type Source Name
disease MESH COVid-19
disease VO vaccination
disease VO vaccinated
disease VO organization
disease VO effectiveness
disease MESH death
disease IDO contact tracing
disease VO effective
drug DRUGBANK Gold
disease IDO acute infection
disease MESH infection

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