Pooling Upper Respiratory Specimens for Rapid Mass Screening of COVID-19 by Real-Time RT-PCR

Abstract

To validate the specimen-pooling strategy for real-time reverse transcription PCR detection of severe acute respiratory syndrome coronavirus 2, we generated different pools including positive specimens, reflecting the distribution of cycle threshold values at initial diagnosis. Cumulative sensitivities of tested pool sizes suggest pooling of <6 specimens for surveillance by this method.

Keywords: COVID-19; SAR-CoV-2; SARS; SARS-CoV-2; SARS-related coronavirus; South Korea; coronavirus disease; real-time PCR; respiratory infections; reverse transcription PCR; severe acute respiratory syndrome; severe acute respiratory syndrome coronavirus 2; specimen pooling; viruses; zoonoses.

Figure 1

Distribution of RdRp gene (C_t) values for specimens from 4,364 confirmed patients in South Korea at their initial diagnosis of coronavirus disease (COVID-19) and the specimens selected by stratified sampling. This figure shows the first RdRp gene C_t values of patients receiving a COVID-19 diagnosis (bars). We selected positive samples with the stratified sampling method based on that distribution (line). Cumulative numbers of selected specimens per stratum are shown. C_t, cycle threshold.

Figure 2

Mean C_t values of RdRp genes of 50 specimens from coronavirus disease patients in South Korea by pool size. The trend line shows logarithmic regression. C_t, cycle threshold.