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. 2020 Feb 4;3(1):14–21. doi: 10.1093/pcmedi/pbaa002

Figure 4 .

Figure 4

The interpretation criteria of 2019-nCoV nucleic acid test results. RT-PCR was used to detect 2019-nCoV. (a) A positive result of RT-PCR: a standard ‘S’-shaped curve for the amplification curves of ORF1ab, N gene, and internal standard control (IC) and a Ct (cycle threshold) value of less than 35. (b) A multiple PCR combined with capillary electrophoresis fragment analysis positive result of 2019-nCoV. (c) An uncertain result: a standard ‘S’-shaped curve and Ct value of less than 35 for IC, no amplification curve of ORF1ab with unrecognizable Ct value, but a standard amplification curve and Ct value of more than 35 of N gene. When an uncertain result occurs, the test should be done again or done by a different method detection. (d) The interpretations of 2019-nCoV RT-PCR results: only when the fluorescent amplification of ORF1ab, N gene/E gene, and IC are all simultaneously positive can the result be reported as 2019-nCoV detection positive. (e) A negative result: standard ‘S’-shaped curve and Ct value of less than 35 for IC, but no amplification curve for ORF1ab and N gene with their Ct value unrecognizable.