San Diego, CA—If pharmacists are asked about loss of sudden loss of taste and smell, the bad news is that the person with the symptoms is fairly likely to have COVID-19 and needs to be referred for evaluation.

The good news, however, is that the case might be more likely to be mild or moderate, according to a new study.

The article in the International Forum of Allergy & Rhinology follows an earlier study validating the loss of smell and taste as indicators of SARS-CoV-2 infection. Now, University of California San Diego Health researchers suggest that the likelihood of a less-serious case with those symptoms could help healthcare providers determine which patients might require hospitalization.

“One of the immediate challenges for health care providers is to determine how to best treat persons infected by the novel coronavirus,” explained first author Carol Yan, MD, 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.”

Dr. Yan pointed out that “Normosmia or the normal sense of smell is an independent predictor of admission in COVID-19 cases. 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,” she added. “If an infected person loses that sense, it seems more likely they will experience milder symptoms, barring other underlying risk factors.”

To determine that, the study team conducted a retrospective review of all patients presenting to a San Diego Hospital system with laboratory-confirmed positive COVID-19 infection, with evaluation of olfactory and gustatory function and clinical disease course.

Between March 3 and April 8, 2020, 169 patients tested positive for COVID-19 disease. Olfactory and gustatory data were obtained for 128/169 (75.7%) subjects of which 26/128 (20.1%) required hospitalization, according to the researchers.

The authors conclude that admission for COVID-19 was associated with intact sense of smell and taste, increased age, diabetes, as well as subjective and objective parameters associated with respiratory failure.

“On adjusted analysis, anosmia was strongly and independently associated with outpatient care (adjusted odds ratio [aOR] 0.09; 95% CI, 0.01-0.74) while positive findings of pulmonary infiltrates and/or pleural effusion on chest radiograph (aOR 8.01; 95% CI, 1.12-57.49) was strongly and independently associated with admission,” the study states.

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, 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 Adam S. DeConde, MD, also a rhinologist and head and neck surgeon.

“Moreover, anosmia was not associated with any other measures typically related to the decision to admit, suggesting that it’s truly an independent factor and may serve as a marker for milder manifestations of COVID-19.”

Dr. DeConde added, “The site and dosage of the initial viral burden, along with the effectiveness of the host immune response, are all potentially important variables in determining the spread of the virus within a person and, ultimately, the clinical course of the infection.”

The authors posit that, if the SARS-CoV-2 virus initially concentrates in the nose and upper airway, where it impacts olfactory function, a less-severe infection could result, decreasing the risk of overwhelming the host immune response, respiratory failure and hospitalization.

“This is a hypothesis, but it’s also similar to the concept underlying live vaccinations,” Dr. DeConde said. “At low dosage and at a distant site of inoculation, the host can generate an immune response without severe infection.”

Loss of smell, he said, might also indicate a robust immune response which has been localized to the nasal passages, limiting effects elsewhere in the body.

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