Zsὁfia Iglὁi, Jans Velzing, Janko van Beek, David van de Vijver, Georgina Aron, Roel Ensing, Kimberley Benschop, Wanda Han, Timo Boelsums, Marion Koopmans, Corine Geurtsvankessel, and Richard Molenkamp
Author affiliations: Erasmus MC, Rotterdam, the Netherlands (Z. Igloi, J. Velzing, J. van Beek, D. van de Vijver, G. Aron, M. Koopmans, C. Geurtsvankessel, R. Molenkamp); Public Health Service Rotterdam-Rijnmond, Rotterdam (R. Ensing, T. Boelsums); National Public Health Institute (RIVM), Bilthoven, the Netherlands (K. Benschop, W. Han)
Figure 1. Comparison of results for rapid antigen detection tests and PCR for diagnosis of severe acute respiratory syndrome coronavirus 2, the Netherlands. A) Example of the 4 grade scaling system used for result readout. Results were determined by the absence or presence of the T band as well as band intensity. An absent T band is read as negative. Positive results were further distinguished as follows: very faint band, +/−; medium intensity band, +; and strong band, ++. Final readout of results was done after the manufacturer’s recommended 15 minutes. B) Correlation of RT-PCR Ct and Ag RDT test band intensity. RT-PCR Ct results were grouped by the 4 categories of the Ag RDT result readout (n = 970). Horizontal line in each box indicates median Ct; box borders indicate 75% interquartile range (IQR), whiskers represent the range of values 1.5 times the IQR, and dots represent individual test results. Ag RDT, antigen rapid detection test; C, control; Ct, cycle threshold; E gene, envelope gene; RT-PCR, reverse transcription pPCR; T, test; −, negative; +/− weak positive; +, positive; ++, strong positive.