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Sudden anosmia: comparative study of intensity and evolution in patients with acute SARS-Cov2 infection and other respiratory viruses

Abstract

Smell represents an important sense that allows humans to understand and interact with the environment. Approximately one third of the sudden loss of smell is caused by an acute viral infection of the upper airways (URTI), usually due to problems in the conduction of odorous molecules to the olfactory fossa, with complete reversal in most cases. Among the clinical presentations of the pandemic caused by SARS-CoV-2 (COVID-19), one that has drawn attention is the olfactory and gustatory changes. According to the first descriptions, the changes in sense of smell have been more intense and of early onset, generally not accompanied by rhinorrhea or nasal obstruction, suggesting a predominant neuroepithelial dysfunction and not an obstructive origin of the olfactory cleft. Another relevant fact is that many patients with COVID-19 have initially manifested themselves only with olfactory changes, even before complaining about other symptoms of greater suspicion, such as fever, odynophagia, cough or dyspnoea. Finally, the olfactory recovery prognosis is not yet fully known in patients affected by COVID-19. In the face of an emerging disease, highly transmissible and of great burden for the health and economy system in global dimensions, the natural history of COVID-19 unfortunately is still poorly known, particularly regarding the smell changes. In this multicenter study involving several Brazilian cities, we propose to prospectively evaluate the evolution of olfaction (measured by quantitative and qualitative smell test - modified CCRC) as well as the positivity of a panel of respiratory viruses in the nasopharynx (detected by PCR, including the SARS-CoV-2) in individuals with sudden anosmia. Furthermore, patients with persistent anosmia after 60 days will be submitted to nasal endoscopy, collection of cells from the olfactory region by scraping (cytobrush) and magnetic resonance imaging. The results of this study will show the prevalence of SARS-CoV-2 in cases of sudden anosmia, identify the positive predictive value of anosmia as a marker of COVID-19, as well as understand the natural history of anosmia in cases of COVID-19 in relation to other viral infections. We hope that the conclusions of this study can assist in the prevention and spread of the disease, as well as guiding patients on the prognosis in relation to the natural behavior of the disease. (AU)