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, respec- tively. 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.