OBJECTIVE: Olfactory dysfunction has been observed as one of the clinical manifestations in COVID-19 patients We aimed to conduct a systematic review and meta-analysis to estimate the overall pooled prevalence of olfactory dysfunction in COVID-19 patients METHODS: PubMed, Scopus, Web of Science, Embase, and Google Scholar databases were searched to identify studies published between 1 December 2019 and 23 July 2020 We used random-effects model to estimate the pooled prevalence with 95% confidence intervals (CIs) Heterogeneity was assessed using the I(2) statistic and Cochran's Q test Robustness of the pooled estimates was checked by different subgroup and sensitivity analyses This study is registered with PROSPERO (CRD42020183768) RESULTS: We identified 1162 studies, of which 83 studies (n=27492, 61 4% female) were included in the meta-analysis Overall, the pooled prevalence of olfactory dysfunction in COVID-19 patients was 47 85% [95% CI: 41 20-54 50] We observed olfactory dysfunction in 54 40% European, 51 11% North American, 31 39% Asian, and 10 71% Australian COVID-19 patients Anosmia, hyposmia, and dysosmia were observed in 35 39%, 36 15%, and 2 53% of the patients, respectively There were discrepancies in the results of studies with objective (higher prevalence) versus subjective (lower prevalence) evaluations The discrepancy might be due to false negative reporting observed in self-reported health measures CONCLUSION: The prevalence of olfactory dysfunction in COVID-19 patients was found to be 47 85% based on high quality evidence Due to the subjective measures of most studies pooled in the analysis, further studies with objective measures are advocated to confirm the finding This article is protected by copyright All rights reserved
Prevalence of olfactory dysfunction in coronavirus disease 2019 (COVID-19): A meta-analysis of 27492 patients