Self-reported alteration of sense of smell or taste in patients with COVID-19: a systematic review and meta-analysis on 3563 patients

Background: Emerging reports suggest that new onset of smell or taste loss are potential early clinical markers of SARS-CoV-2 infection, but it remains unclear as to what extent. Therefore, the purpose of this study is to systematically assess the prevalence of self-reported altered sense of smell or taste in patients with confirmed SARS-CoV-2 infection, overcoming the limitations of individual studies by meta-analysis of pooled data. Methods: The databases Medline, Embase, Web of Science, Scopus and MedRxiv's set were searched from inception to the 4th May 2020. This study was conducted following the PRISMA checklist. Results: 18 studies met the eligibility criteria out of the 171 initially screened citations. The overall prevalence of alteration of the sense of smell or taste was 47%, but estimates were 31% and 67% in severe and mild-to-moderate symptomatic patients, respectively. The loss of smell and taste preceded other symptoms in 20% of cases and it was concomitant in 28%. Conclusions: Based on this meta-analysis, we recommend self-isolation and testing, where possible, for patients complaining smell or taste impairment during COVID-19 pandemic in order to prevent spread of disease and propose the inclusion of loss of smell and taste as recognized symptoms of SARS-CoV-2 in the World Health Organization and other relevant regulatory body's lists.