Relationship of SARS-CoV-2 Antigen and Reverse Transcription PCR Positivity for Viral Cultures

Abstract

We assessed the relationship between antigen and reverse transcription PCR (RT-PCR) test positivity and successful virus isolation. We found that antigen test results were more predictive of virus recovery than RT-PCR results. However, virus was isolated from some antigen-negative and RT-PCR‒positive paired specimens, providing support for the Centers for Disease Control and Prevention antigen testing algorithm.

Keywords: COVID-19; SARS-CoV-2; coronavirus disease; coronaviruses; cycle threshold; rapid antigen test; respiratory infections; reverse transcription PCR; severe acute respiratory syndrome coronavirus 2; viral cultures; viruses; zoonoses.

Figure

Box plots of C_t values among participants with recoverable virus who had concordant positive SARS-CoV-2 RT-PCR and antigen test results (A) compared with those who had positive RT-PCR and negative antigen test results (B), Winnebago County, Wisconsin, USA, November–December 2020. The difference between the 2 groups was significant (p<0.0001). Diamonds indicate means, boxes indicate the first quartile through the third quartile, horizontal bars in boxes indicate medians, and errors bars indicate minimum values to maximum values; outliers are plotted as individual circles. C_t, cycle threshold; RT-PCR, reverse transcription PCR; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.