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

Smell represents an important sense that allows human beings 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 manifestations that have drawn attention during the infection caused by SARS-CoV-2 (COVID-19) are olfactory and gustatory changes. According to the first descriptions, the changes in 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. Faced with an emerging disease, highly transmissible and of great repercussion for the health and economy system in global dimensions, the natural history of COVID-19 is still little known, particularly in terms of smell changes. In this multicenter study involving several Brazilian cities, we propose to prospectively evaluate the evolution of olfaction (measured by quantitative and qualitative test of smell - modified CCRC test) as well as the positivity of a panel of respiratory viruses in the nasopharynx detected by PCR, including SARS-CoV-2) in individuals with sudden anosmia. In addition, patients who continue to complain of anosmia after 60 days will be investigated with nasofibroscopy, collection of cells in the olfactory region (cytobrush) and magnetic resonance imaging. The results of this study may 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 to other viral pictures. We hope that the conclusions of this study can assist in the prevention and dissemination of the disease, as well as guiding patients on the prognosis in relation to the natural behavior of the disease. (AU)