Olfactory and Gustatory Dysfunction in Mild COVID-19

Background: Olfactory and gustatory dysfunction have been reported as characteristic symptoms of coronavirus disease 2019 (COVID-19). This study evaluated olfactory and gustatory dysfunction in mild COVID-19 patients using validated assessment methods. Methods: A prospective surveillance study was conducted for mild COVID-19 patients who were isolated at the Gyeonggi International Living and Treatment Support Center (LTSC), Korea. Olfactory function was assessed using the Korean version of the Questionnaire of Olfactory Disorders (QOD) and Cross-Cultural Smell Identification Test (CC-SIT). Gustatory function was assessed using an 11-point Likert scale and 6-n-propylthiouracil, phenylthiocarbamide, and control strips. All patients underwent nasal and oral cavity endoscopic examination. Findings: Of the 62 patients at the LTSC, 15 patients (24.2%) complained of olfactory or gustatory deterioration on admission. Four of 10 patients who underwent functional evaluation did not have general symptoms and 2 patients were asymptomatic. The mean sQOD-NS and QOD-VAS scores were 13 ± 6 and 4.7 ± 3.6, respectively. The mean CC-SIT score was 8 ± 2. No patients showed anatomical abnormalities associated with olfactory dysfunction on endoscopic examination. The mean Likert scale score for function was 8 ± 2, and there were no abnormal lesions in the oral cavity of any patient. Interpretation: The prevalence of olfactory and gustatory dysfunction was 24.2% in mild COVID-19 patients. All patients had hyposmia due to sensorineural olfactory deterioration, which was confirmed using validated olfactory and gustatory evaluation methods and endoscopic examination. Olfactory and gustatory dysfunction may be characteristic indicators of mild COVID-19. Funding Statement: No funding. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: This study protocol was approved by the Institutional Review Board of the Korea University Ansan Hospital (2020AS0122).