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UC San Diego Health finds loss of smell could be sign of milder cases of COVID-19

"Patients who reported loss of smell were 10 times less likely to be admitted for COVID-19 compared to those without loss of smell," said Dr. Adam DeConde.
Credit: Getty Images/iStockphoto
Olfactory system graphic

SAN DIEGO — Researchers at UC San Diego Health have found that loss of smell related to COVID-19 suggests the resulting illness is more likely to be mild to moderate, a potential early indicator that could help health care providers determine which patients may require hospitalization.

The findings come in the wake of a similar study involving some of the same researchers, who found evidence linking loss of olfactory function to the novel coronavirus.

"One of the immediate challenges for health care providers is to determine how to best treat persons infected by the novel coronavirus," said Dr. Carol Yan, a rhinologist and head and neck surgeon at UC San Diego Health. "If they display no or mild symptoms, can they return home to self-quarantine or will they likely require hospitalization? These are crucial questions for hospitals trying to efficiently and effectively allocate finite medical resources."

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Yan's latest study, conducted with colleagues Drs. Farhoud Faraji, Benjamin Ostrander and Adam DeConde -- all physicians in the Department of Surgery at UC San Diego Health -- and Divya Prajapati, a student in the UC San Diego School of Medicine, suggests loss of smell may be predictive of a milder clinical course of COVID-19.

"Normosmia or the normal sense of smell is an independent predictor of admission in COVID-19 cases," Yan said. "In previous research, we found that loss of olfactory function is a common early symptom, following fever and fatigue. What's notable in the new findings is that it appears that loss of smell may be a predictor that a SARS-CoV-2 infection will not be as severe, and less likely to require hospitalization."

Patients who were hospitalized for COVID-19 treatment were significantly less likely to report anosmia or loss of smell (26.9% compared to 66.7% for COVID-19-infected persons treated as outpatients). Similar percentages were found for loss of taste, known as dysgeusia.

"Patients who reported loss of smell were 10 times less likely to be admitted for COVID-19 compared to those without loss of smell," said senior author DeConde, a rhinologist and head and neck surgeon.

The researchers said the findings -- published online April 24 in the journal International Forum of Allergy & Rhinology -- possibly hint at some of the characteristics of the infection. In other words, if the SARS-CoV-2 virus initially concentrates in the nose and upper airway, where it impacts olfactory function, that may result in an infection that is less severe and sudden in onset, decreasing the risk of overwhelming the host immune response, respiratory failure and hospitalization.

Additionally, more expansive studies are needed for validation, the researchers said, but the findings have important immediate practical applications for health care systems and patients.

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