key: cord-0900999-7dsgs2sd
authors: Zóka, András; Bekő, Gabriella
title: Distinct changes in the real-time PCR detectability of certain SARS-CoV-2 target sequences
date: 2020-05-05
journal: Clin Chim Acta
DOI: 10.1016/j.cca.2020.05.002
sha: 2758e1f695325e6408d3e8ade78110d4abe96ffe
doc_id: 900999
cord_uid: 7dsgs2sd

nan

To the Editor, the recent publication by Lv et al. [1] highlighted notable aspects of the PCR-based diagnosis of SARS-CoV-2 infection, namely that the PCR-based detectability of certain loci might differ significantly and change over time. In our practice we also observed that the SARS-CoV-2 PCR positivity in the oropharyngeal swabs of patients might persist for weeks [2] , however, the characteristics of positivity (including the target sequences detected) may change in a predictable manner. Although the available test kits offer convenient laboratory patients, T-test p<0.01). Our results might indicate that the detectability of the viral Orf1a-related RdRp sequence might fade more rapidly during convalescence, only later followed by the N gene. This phenomenon might affect the interpretation of the results, as detecting a lone N gene might suggest a later presentation within the course of the disease. This trend might also be coherent with the gradual expression of genes encoding different virion components. Orf1 (containing RdRp) is among the earliest sequences transcribed and translated, only later followed by the expression of nucleocapsid and coat protein genes [3] . However, certain patients initially presented with an undetectable RdRp, and subsequently became positive. This might raise the possibility of other causes, including a more unstable nature of the Orf1 RNA sequence or even sampling bias, as a lower quantity of virions might result in losing weak signals. Further, large-scale studies are needed to clarify, whether these observations could be diagnostically utilized.

The authors have no financial or commercial conflict of interest to disclose. 

Dynamic change process of target genes by RT-PCR testing of SARS-Cov-2 during the course of a Coronavirus Disease 2019 patient

Profile of RT-PCR for SARS-CoV-2: a preliminary study from 56 COVID-19 patients

Coronaviruses: An Overview of Their Replication and Pathogenesis