Loss of smell in COVID-19 patients: a critical review with emphasis on the use of olfactory tests
Rosario Marchese‐Ragona, Domenico A. Restivo, Eugenio De Corso, Andrea Vianello, Piero Nicolai, Giancarlo Ottaviano
Abstract
Since December 2019, an outbreak of a newly isolated coronavirus (SARS-CoV-2) appeared in Wuhan, China, and then spread worldwide. Recently, it has emerged that a number of patients may present with sudden hyposmia, sometimes without other symptoms of the disease. We performed a critical review on the methods used to date to investigate the olfactory function in COVID-19 patients in order to establish which should be considered the most appropriate to use during this pandemic. Literature analysis showed that the diagnosis of hyposmia in COVID-19 patients was mainly made through subjective symptomatology collected by questionnaires and/or interview. Psychophysical tests were carried out in a few studies showing signicant discrepancies between the self-reported sense of smell and test results. To date the methods used by authors to investigate smell impairment in COVID-19 patients have been very heterogeneous and predominantly based on self-reported questionnaires leading to confusing and inconclusive results. We suggest that simple validated selfadministered psychophysical olfactory tests could be a valuable instrument to investigate isolated/quarantined or hospitalised COVID-19 patients referring smell impairment in order to conrm olfactory dysfunction.