Quality of early evidence on the pathogenesis, diagnosis, prognosis and treatment of COVID-19.

Since the initial description of the SARS-CoV-2 outbreak and its declaration as a worldwide pandemic, the number of publications on the novel virus has increased rapidly. We studied the trends and quality of evidence in early SARS-CoV-2 publications. A comprehensive search of MEDLINE and EMBASE was performed for papers published between 1 January 2020 and 21 April 2020. Two reviewers independently screened titles and abstracts and subsequently full texts for eligibility in this systematic review. The search yielded 2504 citations published between January and February 2020 or an unspecified date, 109 of which remained for extraction after screening. Data extracted included study design, year of publication, country of basis, journal of publication, impact factor of publishing journal, study sample size, number of citations and topic of investigation. Study design-specific critical appraisal tools were used to evaluate the scientific rigour of all included papers: the Joanna Briggs Institute checklist was used for case series, Scale for the Assessment of Narrative Review Articles scale for narrative reviews, Newcastle-Ottawa scale for cohort studies and AMSTAR 2 for systematic reviews. The overall quality of the literature was low-moderate. Of 541 papers that reported clinical characteristics, 295 were commentaries/expert opinions and 36 were case reports. There were no randomised clinical trials, 45 case series studies, 58 narrative reviews, 1 cohort study and 5 systematic reviews. We encourage clinicians to be attentive to these findings when utilising early SARS-CoV-2 evidence in their practices. © Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.