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Table 3 The characteristics of included systematic reviews regarding the olfactory and oral dysfunction of COVID-19 infection

From: Neurological manifestations of COVID-19 infection: an umbrella review

Authors Origin Type Quality Number of included studies Types of included studies Assessing the quality of included studies Searched databases Main results
1. Borsetto et al. 2020 [46] Critically Low Systematic Review + Meta-analysis UK 18 Not mentioned None Embase, Scopus, Web of Science, Medline, MedRxiv The alteration of the sense of smell or taste was estimated 31% in severe and 67% in mild-to-moderate symptomatic patients
2. da Costa et al. 2020 [61] Moderate Systematic Review Brazil 6 Cohort, cross sectional, case–control NOS1 Pubmed, Scopus, Google Scholar, Cochrane library, LILACS2, Science direct OGD3 occurs at varying intensities and prior to the general symptoms of COVID-19
3. Samaranayake et al. 2020 [62] Moderate Systematic Review United Arab Emirates 8 Cohort, cross sectional, case–control Nine-item checklist for prevalence study Pubmed, Web of Science, EBSCO Anosmia and dysgeusia symptoms were present in both ambulatory and hospitalized patients and mild-to-severe cases of COVID-19
4. Lechner et al. 2020 [45] Critically Low Systematic Review UK 31 Case series, case reports, cross sectional None Pubmed OGD is indicative of COVID-19 infection and should be implicated in evaluation of healthcare workers
5. Rocke et al. 2020 [47] Moderate Systematic Review + Meta-analysis UK 12 Case series, cross sectional, case–control ROBINS‐E Pubmed, Embase, Cochrane library, HMIC, MedRxiv There is a significant evidence demonstrating an association between olfactory dysfunction and COVID‐19
6. Zahra et al. 2020 [57] Moderate Systematic Review UK 23 Cohort, case series, cross sectional, case–control NOS Pubmed, Scopus, Google Scholar, Cochrane library, Medline Symptoms of anosmia and dysgeusia were frequently reported by COVID-19-positive patients; more commonly in females and in younger patients
7. Fuccillo et al. 2020 [58] Moderate Systematic Review Italy 32 Cohort, case series, cross sectional NHLBI4 Assessment Tools, Oxford CEBM5 guide Pubmed, Embase, Web of Science Olfactory disorders represent an important clinical characteristic of COVID-19
8. Hoang et al. 2020 [48] Moderate Systematic Review + Meta-analysis Thailand 14 Case series, cross sectional, case–control Modified NOS Pubmed, Embase, Scopus, Medline OVID OGD and COVID-19 are associated
9. Tong et al. 2020 [49] Moderate Systematic Review + Meta-analysis USA 10 Cohort, case series, cross sectional, case–control The quality assessment checklist for prevalence studies adapted from Hoy et al. Pubmed, Scopus OGS are common symptoms in patients with COVID-19 and may be manifested as an early symptoms in the clinical course of the COVID-19 infection
10. Passarelli et al. 2020 [59] Critically Low Systematic Review Italy 5 Not mentioned None Pubmed Anosmia and ageusia are a significant sign and can be considered as the first manifestation of the infection
11. Agyeman et al. 2020 [50] Moderate Systematic Review + Meta-analysis Australia 24 Not mentioned Murad tool Pubmed, Embase, Medline, MedRxiv High prevalence of OGD among patients infected with COVID-19 are reported across the literature
12. Pang et al. 2020 [51] Moderate Systematic Review + Meta-analysis Singapore 19 Cohort, case series, cross sectional, case–control The risk of bias tool for prevalence studies by Hoy et al. Pubmed Patient-reported olfactory dysfunction is a highly specific manifestation of COVID-19
13. Hajikhani et al. 2020 [52] Moderate Systematic Review + Meta-analysis Iran 15 Not mentioned JBI6 tool Pubmed, Embase, Web of Science OGD in patients with confirmed COVID-19 have a high prevalence
14. Sedaghat et al. 2020 [60] Critically Low Systematic Review USA 6 Not mentioned None Pubmed, Embase, Web of Science OGD is highly common in the course of COVID-19 infection and patients may experience sudden-onset of smell alteration as the first symptom
15. Chi et al. 2020 [53] Low Systematic Review + Meta-analysis China 12 Not mentioned None Pubmed, Embase, Cochrane library, Cumulative Index to Nursing and Allied Health Literature, National Digital Library of Theses and Dissertations in Taiwan database, Art Image Indexing Service on the Internet Database (Chinese database) OGD is associated with COVID-19 infection and in some patients is the first symptom of the infection
16. Giorli et al. 2020 [54] Critically Low Systematic Review + Meta-analysis Italy 11 Cohort, cross sectional, case–control None Pubmed, Scopus, Web of Science New onset olfactory dysfunction is associated with COVID-19, anosmia is more frequent in non-hospitalized COVID-19 patients than in hospitalized ones
17. Ibekwe et al. 2020 [55] Moderate Systematic Review + Meta-analysis Nigeria 32 Cohort, cross sectional, case–control JBI tool Pubmed, Embase, Google Scholar, Web of Science The prevalence of smell and taste loss among COVID-19 patients was high globally
18. Chung et al. 2020 [56] Critically Low Cohort + Systematic Review China 23 Cohort, experimental, case series, case reports None Pubmed COVID-19-related smell disturbance can be severe and prolonged and may be the only symptom
19. Printza et al. 2020 [63] Critically Low Systematic Review Greece 24 Cohort, case series, cross sectional, case–control None Pubmed, Cochrane library, MedRxiv Anosmia is more prevalent in COVID-19 patients than in patients suffering from other respiratory infections or controls
  1. 1. NOS: Newcastle–Ottawa Scale, 2. LILACS: Latin American and Caribbean Health Sciences Literature; 3. OGD: Olfactory and Gustatory Dysfunctions; 4. NHLBI: National Heart, Lung, and Blood Institute; 5. CEBM: Center for Evidence-Based Medicine; 6. JBI: Joanna Briggs Institute