Nationwide External Quality Assessment of SARS-CoV-2 Molecular Testing, South Korea

T he current outbreak of coronavirus disease (CO- VID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to spread.As of June 27, 2020, the pandemic had affected 214 countries, resulting in 9,653,048 recorded cases and 491,128 deaths (1,2).Early detection of SARS-CoV-2 and immediate isolation of infected patients from the susceptible population is important for preventing the spread of infection (3).Real-time reverse transcription PCR (rRT-PCR) is currently the most reliable method for diagnosing COVID-19 (4).Since March 2, 2020, the number of newly reported cases in South Korea appears to be declining; the mean number of daily new confirmed cases decreased to 40 by the end of June (5).Intensive SARS-CoV-2 testing helped to contain the spread of the disease in South Korea.Since March 1, South Korea (population ≈51 million) has performed ≈20,000 tests per day by using rRT-PCR.The outstanding achievements of the public health response were attributable to the rapid expansion of diagnostic testing capabilities resulting from the collaboration between the public and private sectors.In June 2016, South Korea enacted emergency use authorization (EUA) legislation with the aim of supplying commercial kits to meet the demands of nongovernmental clinical laboratories and to guarantee quality assurance through mandatory technical training regarding standardized laboratory guidelines and external quality assessment (EQA) (6).As of March 31, after successfully completing a proficiency testing panel consisting of 7-plasmid DNA specimens, a total of 95 nongovernmental clinical laboratories were conducting SARS-CoV-2 tests by using 5 different EUA kits (6).However, the nucleic acid extraction methods, rRT-PCR reagents, and thermocyclers used differed among laboratories.EQAs using pooled respiratory samples spiked with inactivated cultured SARS-CoV-2 had indicated the possible effects of these variations on assay performance, thereby allowing Nationwide External Quality Assessment of SARS-CoV-2 Molecular Testing, South Korea