Analytical and Clinical Validation of Six Commercial Middle East Respiratory Syndrome Coronavirus RNA Detection Kits Based on Real-Time Reverse-Transcription PCR

Kim, Mi-Na; Ko, Young Jin; Seong, Moon-Woo; Kim, Jae-Seok; Shin, Bo-Moon; Sung, Heungsup

The LODs for upE varied from 21.88 to 263.03 copies/reaction, and those of ORF1a varied from 6.92 to 128.82 copies/reaction (Fig. 1) . According to the probit regression analysis, the 95% confidence intervals (CI) for upE and ORF1a were found to overlap among the tested kits, with the exception of ORF1a by the PowerChek kit (Fig. 2) . The LODs for upE using both the single and multiple gene-targeting formats of the 2-step kits were 1.64 and 1.45 log copies/reaction for the PowerChek kit and 1.76 and 1.61 log copies/reaction for the DiaPlexQ kit (Fig. 2 ). The LOD for upE was 1.34 log copies/reaction for the Any-plex kit, but no CI value could be calculated because there were no positive reactions at 1.0 log copy/reaction, while all 16 replicate specimens were positive at 1.5 log copies/reaction. In contrast, although the LODs for upE and ORF1a using the LightMix kit were 2.11 log copies/reaction and 1.78 log copies/reaction, respectively, trailing of positives was observed at much lower concentrations than these LODs (Fig. 1) . The LODs for upE of three different 1-step kits, the AccuPower, Light Mix, and Ultrafast kits, were > 2.0 log copies/reaction, which was less sensitive than those of three different 2-step kits; however, this difference was not significant (Fig. 2) . The LODs for ORF1a varied less-i.e., from 1.78 to 2.11 log copies/reaction-with the exception of the PowerChek kit, which was considerably lower at 0.84 log copies/reaction (Fig. 2) . None of the kits tested in this study showed cross-reactivity with other respiratory viruses.