External Quality Assessment of MERS-CoV Molecular Diagnostics During the 2015 Korean Outbreak

Seong, Moon-Woo; Lee, Seung Jun; Cho, Sung Im; Ko, Kyungphil; Kim, Mi-Na; Sung, Heungsub; Kim, Jae-Seok; Ahn, Ji Soo; Yu, Byung Su; Kim, Taek Soo; Kim, Eui Chong; Park, Sung Sup

In this survey, most participants used commercial rRT-PCR kits. Our results showed that significantly different CT values could be produced depending on the kit used. Though these kits are for semi-quantitative purposes and a difference in CT values does not correlate with differences in analytical sensitivity, a large difference in the CT values for the same material may influence the analytical sensitivity of the kit. Therefore, cut-off values should be carefully validated for each method in order to have optimal sensitivity for the detection of MERS-CoV in clinical settings. In addition, our study demonstrates that CT values might be different depending on the platform used for performing real-time PCR, even when using the same commercial kit. Therefore, the platform as well as the kit should be considered when establishing or validating the cut-off value of a kit. It is known that the analytical sensitivity of MERS-CoV RT-PCR depends on the target gene tested; the ORF1a assay has a lower sensitivity compared with the upE assay [3] . In this survey, all participants reported both upE and ORF1a results. Both assays gave comparable results, and no significant difference between them was observed.