[Journal of Clinical Microbiology] Improved molecular diagnosis of COVID-19 by the novel, highly sensitive and specific COVID-19-RdRp/Hel real-time reverse transcription-polymerase chain reaction assay validated in vitro and with clinical specimens

04/03/2020

Journal of Clinical Microbiology, 4 March 2020

Jasper Fuk-Woo Chan, Cyril Chik-Yan Yip, Kelvin Kai-Wang To, Tommy Hing-Cheung Tang, Sally Cheuk-Ying Wong, Kit-Hang Leung, Agnes Yim-Fong Fung, Anthony Chin-Ki Ng, Zijiao Zou, Hoi-Wah Tsoi, Garnet Kwan-Yue Choi, Anthony Raymond Tam, Vincent Chi-Chung Cheng, Kwok-Hung Chan, Owen Tak-Yin Tsang, Kwok-Yung Yuen

Highlights:

Highly sensitive and specific laboratory diagnostics are important for controlling the rapidly evolving SARS-CoV-2-associated Coronavirus Disease 2019 (COVID-19) epidemic.
In this study, we developed and compared the performance of three novel real-time RT-PCR assays targeting the RNA-dependent RNA polymerase (RdRp)/helicase (Hel), spike (S), and nucleocapsid (N) genes of SARS-CoV-2 with that of the reported RdRp-P2 assay which is used in >30 European laboratories.
Among the three novel assays, the COVID-19-RdRp/Hel assay had the lowest limit of detection in vitro (1.8 TCID₅₀/ml with genomic RNA and 11.2 RNA copies/reaction with in vitro RNA transcripts).
Among 273 specimens from 15 patients with laboratory-confirmed COVID-19 in Hong Kong, 77 (28.2%) were positive by both the COVID-19-RdRp/Hel and RdRp-P2 assays. The COVID-19-RdRp/Hel assay was positive for an additional 42 RdRd-P2-negative specimens [119/273 (43.6%) vs 77/273 (28.2%), P<0.001], including 29/120 (24.2%) respiratory tract specimens and 13/153 (8.5%) non-respiratory tract specimens.
The mean viral load of these specimens was 3.21×10⁴ RNA copies/ml (range, 2.21×10² to 4.71×10⁵ RNA copies/ml).
The highly sensitive and specific COVID-19-RdRp/Hel assay may help to improve the laboratory diagnosis of COVID-19.