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Testing for Decreased Smell Function May Help Identify Coronavirus Patients Earlier

by Linda Kossoff •

Could olfactory testing on COVID-19 patients help identify individuals in need of early treatment or quarantine?

Bottom Line: Decreased smell function is a major marker for SARS-CoV-2 infection; therefore, smell testing may help to identify COVID-19 patients in need of early treatment or quarantine.

Commentary: “This is the only study in which quantitative olfactory testing has actually been performed in a cohort of confirmed SARS-CoV-2 infected patients, demonstrating that 59 of 60 patients exhibited demonstrable smell loss, with over half having anosmia or severe microsmia. Only 35% of the patients were aware of the loss, emphasizing the limitations of self-reports of smell dysfunction—a limitation well known in the chemosensory literature.” —Timothy Smith, MD

Background: Numerous reports cited in media indicate that anosmia occurs in persons who contracted COVID-19 by exposure to the SARS-COV-02 virus. Validated quantitative olfactory testing has not been performed in a cohort of COVID-19 patients. Therefore, the proportion of affected patients, and the magnitude of their deficits, is not known.

Study design: Case-control study.

Setting: Masih Daneshvari Hospital and Institute for Research in Fundamental Sciences, Tehran, Iran.

Synopsis: Researchers administered the Persian version of the 40-odorant University of Pennsylvania Smell Identification Test to 60 hospitalized COVID-19 patients in the disease recovery period, plus 60 matched controls, to assess the presence, magnitude, and frequency of olfactory dysfunction. Clinical severity was classified as mild, moderate, or severe according to Massachusetts General Hospital COVID-19 treatment guidance for treatment algorithm. Epidemiological risk factors included age > 55 years and hypertension/cardiovascular, pulmonary or kidney disease, as well as compromised immunity. Results showed that 98% of the COVID-19 patients exhibited marked olfactory dysfunction seemingly independent of severe nasal congestion or inflammation, and 58% were either anosmic or severely microsmic. In contrast, of the 60 controls, 82% were normal and 18% had only mild dysfunction. The major limitation is the sample of the study population at only one point in time relative to the onset of COVID-19 symptoms.

Citation: Moein ST, Hashemian SMR, Mansourafshar B, et al. Smell dysfunction: a biomarker for COVID-19 [published online ahead of print April 17, 2020]. Int Forum Allergy Rhinol. doi:10.1002/air.22587.