Smell and Taste Dysfunction in Patients With COVID-19: A Systematic Review and Meta-analysis

Agyeman, Akosua Adom; Lee Chin, Ken; Landersdorfer, Cornelia B.; Liew, Danny; Ofori-Asenso, Richard

Abstract Objective To estimate the prevalence of olfactory and gustatory dysfunctions (OGDs) among patients infected with novel coronavirus disease 2019 (COVID-19). Patients and Methods A systematic review was conducted by searching MEDLINE, EMBASE, and the preprint server MedRxiv until 11 May 2020 using the terms ‘anosmia’ or ‘hyposmia’ or ‘dysosmia’ or ‘olfactory dysfunction’ or ‘olfaction disorder’ or ‘smell dysfunction’ or ‘ageusia’ or ‘hypogeusia’ or ‘dysgeusia’ or ‘taste dysfunction’ or ‘gustatory dysfunction’ or ‘neurological’ and ‘COVID-19’ or ‘2019 novel coronavirus’ or ‘2019-nCoV’ or ‘SARS-CoV-2’. References of included studies were also manually screened. Only studies involving diagnostic-confirmed patients with COVID-19 were included. Random-effects meta-analysis was performed. Results A total of twenty-four studies with data from 8438 test-confirmed COVID-19 patients from thirteen countries were included. The pooled proportion of patients presenting with olfactory and gustatory dysfunctions was 41.0% (95% confidence interval [CI] 28.5% to 53.9) and 38.2% (95% CI 24.0 to 53.6%), respectively. Increasing mean age correlated with lower prevalence of olfactory (coefficient = -0.076; p=.02) and gustatory (coefficient = -0.073; p=.03) dysfunctions. There was a higher prevalence of olfactory dysfunctions with the use of objective measurements compared to self-reports (coefficient = 2.33; p=.01). No significant moderation of the prevalence of OGDs by gender was observed. Conclusion There is a high prevalence of OGDs among patients infected with COVID-19. Routine screening for these conditions could contribute to improved case detection in the ongoing COVID-19 pandemic. However, to better inform population screening measures, further studies are needed to establish causality.