Olfactory and gustatory dysfunctions in COVID-19 patients: A systematic review and meta-analysis.

Olfactory and gustatory dysfunctions (OGD) are pathognomonic symptoms in patients with Coronavirus Disease 2019 (COVID-19). This study reviews the associations of OGD with COVID-19 which will be useful for early diagnosis and self-isolation. Systematic searches of PubMed, Ovid Medline, Scopus, and EMBASE electronic databases were performed. Studies reporting OGD in COVID-19 patients were included. Data were pooled for meta-analysis. The outcomes were odds ratios (OR) of OGD in COVID-19 patients. Proportions of smell and/or taste dysfunctions in the COVID-19 patients were assessed. Fourteen studies (21,515 participants, age 49.12 years, 26% male) were included. The OR of olfactory and/or gustatory dysfunctions in COVID-19 patients were 11.26 (95% confidence interval (CI) 5.41 to 23.4) when compared with acute respiratory infection (ARI) without detectable virus and 6.46 (95% CI 2.79 to 14.97) in patients with other respiratory viruses. The OR of olfactory dysfunction in COVID-19 patients were 11.67 (95% CI 6.43 to 21.17) when compared with the ARI patients without detectable virus and 4.17 (95% CI 1.34 to 12.98) with other respiratory viruses. The OR of gustatory dysfunction in COVID-19 patients were 12.70 (95% CI 7.9 to 20.44) when compared with the ARI patients without detectable virus and 4.94 (95%CI 1.59 to 15.31) with other respiratory viruses. Fifty percent (95% CI 36.7 to 63.3%) of COVID-19 patients had olfactory and/or gustatory dysfunctions. In summary, there are associations between OGD and COVID-19 patients. Patients presenting with ARI should be assessed for olfactory and gustatory functions.

Smell and taste dysfunction in patients with SARS-CoV-2 infection: A review of epidemiology, pathogenesis, prognosis, and treatment options.

During the initial pandemic wave of COVID-19, apart from common presenting symptoms (cough, fever, and fatigue), many countries have reported a sudden increase in the number of smell and taste dysfunction patients. Smell dysfunction has been reported in other viral infections (parainfluenza, rhinovirus, SARS, and others), but the incidence is much lower than SARS-CoV-2 infection. The pathophysiology of post-infectious olfactory loss was hypothesized that viruses may produce an inflammatory reaction of the nasal mucosa or damage the olfactory neuroepithelium directly. However, loss of smell could be presented in COVID-19 patients without other rhinologic symptoms or significant nasal inflammation. This review aims to provide a brief overview of recent evidence for epidemiology, pathological mechanisms for the smell, and taste dysfunction in SARS-CoV-2 infected patients. Furthermore, prognosis and treatments are reviewed with scanty evidence. We also discuss the possibility of using "smell and taste loss" as a screening tool for COVID-19 and treatment options in the post-SARS-CoV-2 infectious olfactory loss.