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

2022; Elsevier BV; Volume: 105; Issue: 1 Linguagem: Inglês

10.1016/j.diagmicrobio.2022.115805

1879-0070

Mikel Joseba Urrutikoetxea Gutiérrez, Paloma Liendo Arenzana, Domingo Fernández Vecilla, Mari Carmen Nieto Toboso, Estíbaliz Ugalde Zarraga, Mikele Macho Aizpurua, José Luis Díaz de Tuesta del Arco,

Advanced biosensing and bioanalysis techniques

The objective of this study was to compare the numeric cut-off index (COI) of automated antigen tests with the cycle-threshold (Ct) value.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 0.6 and 1 were considered indeterminate and overproved by RT-PCR.From 13,937 samples 7944(57%) were positive and 189(1.35%) indeterminate. There was a strong correlation between Cts and COI values at the positive samples, but that was not the case for indeterminates.COI values of the positive samples (COI >1) are comparable to Ct values and may therefore be used as proxy viral loads, however this is not the case for indeterminate samples.