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Abstract Background Because of the rapid spreading of severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2) infection, the Coronavirus disease 2019 (COVID-19) outbreak was characterized as a pandemic by the WHO on March 11, 2020. Materials and Methods Following the PRISMA statement guidelines, we conducted this systematic review and meta-analysis according to the Cochrane handbook of systematic reviews of intervention. We searched PubMed, Scopus, Cochrane, and Web of Science, Embase, and Science Direct till December 2021 with relevant keywords. We included the whole clinical studies assessing olfactory and/or gustatory dysfunctions (OGD) in patients with COVID-19, studies including patients with a confirmed diagnosis of COVID-19 by a positive result of RT-PCR were included, studies that assessed the OGD by either subjective evaluation were also included, studies written in English languages only, all of the studies must have been written in English as a full-text manuscript, double or single-arm designs. Results A total of 12 studies were finally included for the final qualitative and quantitative analysis illustrating the association and the relationship between COVID-19 infection and olfactory and gustatory functions. The mean age of the participants was 49.12 years. The pooled analysis of the included studies showed a significant association of positive results between OGD and COVID-19 infection. Also, the analysis showed a significant association of positive results between either isolated olfactory or gustatory dysfunction and COVID-19 infection. Regarding the association between gustatory dysfunction in COVID-19 patients versus (Acute respiratory infection) ARI patients with no detectable virus, the analysis showed a significant difference between COVID-19 patients and ARI patients with no detectable virus regarding the gustatory dysfunction meaning there is a high association between gustatory dysfunction and COVID-19 patients other than ARI patients with no detectable virus. Finally, the pooled analysis of the included studies showed a significant difference between COVID-19 patients and ARI patients with other respiratory viruses (ORV) in terms of OGD. Conclusion Based on the available evidence, there are regional and chronological differences in the prevalence rates of olfactory and gustatory dysfunction. Future studies, particularly those that document the temporal relationship in the onset of these 2 symptoms, are needed.
Sabra et al. (2024) studied this question.