Evaluation of Olfactory Function With Objective Tests in COVID-19-Positive Patients: A Cross-Sectional Study

Olfactory dysfunction is relatively high in coronavirus disease 2019 (COVID-19) patients. The aim of this study is to investigate the incidence of olfactory disorder objectively in patients with laboratory-confirmed COVID-19 infection.

The study included 31 healthy controls and 59 COVID-19 patients who were diagnosed and treated in the COVID departments in a tertiary hospital. The patients with corona virus infection were screened by a questionnaire and were classified into 2 groups as either group 2 (patients without self-reported smell loss) or group 3 (patients with self-reported smell loss). Age and gender matched healthy controls who do not have chronic nasal condition or nasal surgery history comprised the control group (group 1). All of the patients and subjects in the control group were tested by the Sniffin' Sticks test. All of the answers and scores were recorded, and the comparisons were made.

The rate of self-reported smell and taste loss in all COVID-19 patients in this study was 52.5% and 42%, respectively. There was a significant difference in threshold, discrimination, identification, and Threshold, Discrimination, Identification (TDI) scores between groups 1 and 2. When the comparisons between group 1 and 3 were made, again threshold, discrimination, identification, and TDI scores were significantly different. The comparison between groups 2 and 3 demonstrated a significant difference in discrimination, identification, and TDI scores, but threshold score was not different statistically. With questionnaire, the rate of olfactory dysfunction in COVID-19 patients was 52.5%, but with objective test, the rate was calculated as 83%.

Olfactory and gustatory dysfunctions are common in COVID-19 patients. According to findings with the objective test method in this study, smell disorder in COVID-19 patients was much higher than those detected by questionnaires.