RT-PCR for SARS-CoV-2: quantitative versus qualitative

We read the Article by Lescure and colleagues1Lescure FX Bouadma L Nguyen D et al.Clinical virological data of first cases COVID-19 in Europe: a case series.Lancet Infect Dis. 2020; (published online March 27.)https://doi.org/10.1016/S1473-3099(20)30200-0Summary Full Text PDF PubMed Scopus (746) Google Scholar with great interest. During ongoing coronavirus disease 2019 (COVID-19) pandemic, monitoring patients infected severe acute respiratory syndrome 2 (SARS-CoV-2) using viral kinetics or loads various sample types real-time RT-PCR has become essential. However, understanding whether test results are interpreted as quantitative, qualitative, semi-quantitative is important. Since cycle threshold (Ct) values from can be affected batch effect, variations among different runs need to closely monitored laboratories—especially for quality control quantitative RT-PCR. Unfortunately, several papers on use naive Ct qualitative quantitation unit ΔCt incorrect unit.2Zou Ruan F Huang M al.SARS-CoV-2 load upper specimens patients.N Engl J Med. 382: 1177-1179Crossref (3211) Scholar, 3Shen C Wang Z Zhao al.Treatment 5 critically ill convalescent plasma.JAMA. 27.)DOI:10.1001/jama.2020.4783Crossref (1623) Quantitative entirely value itself cannot directly without standard curve reference materials. Thorough evaluation reliability robustness key accurately quantify expected copy number. There wide heterogeneity inconsistency curves calculated studies that provided serial dilution samples estimated (figure).2Zou 4Chu DKW Pan Y Cheng SMS al.Molecular diagnosis novel (2019-nCoV) causing an outbreak pneumonia.Clin Chem. 66: 549-555Crossref (836) 5Chan JF Yip CC To KK al.Improved molecular novel, highly sensitive specific COVID-19-RdRp/Hel reverse transcription-polymerase chain reaction assay validated vitro clinical specimens.J Clin Microbiol. 58: e00310-e00320Crossref (655) An appropriate adequate limit detection required quantification correctly track titre kinetics. A two-step approach (for detection) quantification) recommended focusing loads, clearly presented colleagues.1Lescure Furthermore, units according types—ie, copies per 1000 cells samples), mL plasma), g stool)—should followed clinicians, outstandingly shown When interpreting SARS-CoV-2 RT-PCR, validity materials in-house plasmid controls known numbers should confirmed interpret loads. In conclusion, precautions needed when publications avoid misunderstanding comparison across studies. declare no competing interests. MSH JHR contributed study design, collection, analysis, interpretation, literature search, writing Correspondence. J-HB YC interpretation. All authors reviewed approved final version Clinical seriesWe illustrated three biological evolution five detailed comprehensive sampling strategy. believe these findings will contribute better natural history advances implementation more efficient infection strategies. Full-Text