Performance of a Point-of-Care Test for the Rapid Detection of SARS-CoV-2 Antigen
Annabelle Strömer, Ruben Rose, Miriam R. Schäfer, Frieda Schön, Anna Vollersen, Thomas Lorentz, Helmut Fickenscher, Andi Krumbholz
Abstract
The rapid detection of infections caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is necessary in the ongoing pandemic. Antigen-specific point-of-care tests (POCT) may be useful for this purpose. Here, such a POCT (SARS-CoV-2 NADAL® COVID-19 Ag) was compared to a laboratory-developed triplex real-time polymerase chain reaction (RT-PCR) designed for the detection of viral nucleoprotein gene and two control targets. This RT-PCR served as a reference to investigate POCT sensitivity by re-testing upper respiratory tract (URT) samples (n = 124) exhibiting different SARS-CoV-2 loads in terms of RT-PCR threshold cycle (Ct) values. The optical intensities of the antigen bands were compared to the Ct values of the RT-PCR. The infectivity of various virus loads was estimated by inoculating Vero cells with URT samples (n = 64, Ct 17-34). POCT sensitivity varied from 100% (Ct < 25) to 73.1% (Ct ≤ 30); higher SARS-CoV-2 loads correlated with higher band intensities. All samples with a Ct > 30 were negative; among SARS-CoV-2 free samples (n = 10) no false-positives were detected. A head-to-head comparison with another POCT (Abbott, Panbio™ COVID-19 Ag Rapid Test) yielded similar results. Isolation of SARS-CoV-2 in cell-culture was successful up to a Ct value of 29. The POCT reliably detects high SARS-CoV-2 loads and rapidly identifies infectious individuals.