COI vs Ct: comparing automated antigen tests cut-off index (COI) to PCR cycle threshold (Ct).

Introduction: The objective of this study was to compare the numeric cut-off index (COI) of automated antigen tests with the cycle-threshold (Ct) value.

Materials And Methods: COI values of all samples processed with the Elecsys® SARS-CoV-2 Antigen (Roche, Switzerland) from January to February 2022 were retrieved and the positive were compared to RdRP Cts of Allplex Variants I (Seegene, Korea). COI between 0.