Concrete objectives on discrete data are a prerequisite for a scientific publication
We studied the research article recently published by Zheng et al  with much interest, which highlights the important aspects of Covid-19 and its causative agent. The study aims to contribute to and enhance our understanding about the circulation of the SARS-CoV-2 in various tissues/excretions of patients, disease progression and its management in the long run. Importantly, this study highlights the presence of the virus in patient’s stool, which brings new insights into epidemic management and surveillance. Overall the study is well conceived and paves the way for further research.
But, being important, the study has some apparently contrasting facts and figures, which affects the overall conclusion and questions the quality of the study. Here we want to document those points; summary below.
First, the ‘title’ indicates a study conducted in Zhejiang province from ‘January to March, 2020’ (03 months) while the ‘objective’ section of the ‘abstract’ mentions that the study is conducted between the ‘first four months of the epidemic in Zhejiang province, China’, contrary to the time period in the title of the article. This should be revisited in order to have a clear picture.
Second, again, under the ‘participants’ heading in the ‘abstract’, it is mentioned that ‘data were collected from 19 January 2020 to 20 March 2020’ which is consistent with the title of the article but contrary to the subsequent ‘method section’. It is mentioned in the ‘methods’ section that ‘this was a retrospective cohort study of patients with laboratory confirmed covid-19 admitted consecutively to the First Affiliated Hospital, College of Medicine, Zhejiang University from 19 January 2020 to 15 February 2020’, which is confusing for readers.
Third, the supplementary figure S2 with legend, ‘the daily samples collection of different sample types by days from illness’ indicating the total time span of the study is 66 days.
On the basis of these factors, we have three different types of temporal data the article seems to be based on: from January 19 to February 15 (28 days in total), from January 19 to March 20 (62 days in total) and S2 figure (66 days in total). The different figures raise doubts on the quality of the article and the conclusion drawn. In such a scenario, for example, the time period of recovery of the SARS-CoV-2, its copy number/load in various samples/excretions and subsequently the implications of this study for disease diagnosis and management could not be drawn. Thus, we suggest that these issues be noted and be addressed so that the quality and integrity of the study is not in doubt on the important current problem of Covid-19.
Zheng S, Fan J. Yu F, et al., Viral load dynamics and disease severity in patients infected with SARS-CoV-2 in Zhejiang province, China, January-March 2020: retrospective cohort study. BMJ. 2020;369:m1443. doi: 10.1136/bmj.m1443
Competing interests: No competing interests