Validation of a Rapid Antigen Test as a Screening Tool for SARS-CoV-2 Infection in Asymptomatic Populations. Sensitivity, Specificity and Predictive Values

Background: Early diagnosis of SARS-CoV-2 infection is essential to reduce disease spread. Rapid antigen tests have not been sufficiently evaluated in asymptomatic patients to be used as massive population screening tools. Methods: Head-to-head evaluation of Roche rapid antigen test as a SARS-CoV-2 screening tool in asymptomatic adults from a semi-closed community. Sensitivity, specificity and predictive values were calculated using RT-PCR as reference method . Findings: Roche-rapid test was performed on 2542 asymptomatic adults in a community with a SARS-CoV-2 incidence of 1.93%. It showed a sensitivity of 71.43% (IC 95%: 56.74 – 83.42) and a specificity of 99.68% (IC 95%: 99.37 - 99.86). Positive Predictive Value was 81.4 (IC95% 66.6 – 91.61) and Negative Predictive Value was 99.44 (IC 95% 99.06 – 99.69). Test sensitivity was related to viral load, with higher sensitivity in RT-PCR Ct values under 25 (93.75%, IC 95%: 71.96 – 98.93), that dropped to 29.41% (IC 95%: 10.31- 55.96) in RT-PCR Ct values above 25.  Interpretation: This study demonstrates that rapid antigen tests are less effective in asymptomatic population, and therefore are not useful for widespread testing, due to the potential false-negative results and their consequences. Funding: This research received no external funding. Roche Diagnostics S.L. provided the rapid antigen tests required for the study. Declaration of Interest: None to declare. Ethical Approval: Approved by the University of Navarra Ethics committee