J Korean Med Sci.  2021 Jun;36(22):e161. 10.3346/jkms.2021.36.e161.

Clinical Features of Olfactory Dysfunction in COVID-19 Patients

• Seo MY
• Choi WS
• Lee SH

• KMID: 2516582
• DOI: http://doi.org/10.3346/jkms.2021.36.e161

Abstract

Background
The aim of this study was to evaluate the subjective and objective olfactory function in coronavirus disease 2019 (COVID-19) patients and the effect of olfactory training.
Methods
A prospective cohort study was performed in 53 patients who recovered from COVID-19 and visited our tertiary hospital. Subjective olfactory function was evaluated using the 11-point Likert scale (0–10) and the Korean version of the Questionnaire of Olfactory Disorders (QOD). Objective olfactory function was evaluated using Cross-Cultural Smell Identification Test (CC-SIT). Confirmed patients were followed up after 2 months of olfactory training.
Results
The median, interquartile range (Q1–Q3) score of subjective olfactory function significantly deteriorated in patients with olfactory dysfunction (OD) than in those without OD, even after 3 months of onset (11-point Likert scale, 8, 6–9 vs. 10, 10–10; short version of QOD-negative statements, 19, 16–21 vs. 21, 21–21; QOD-visual analogue scale, 7, 1–13 vs. 0, 0–0; all P < 0.001). However, the objective olfactory function was not significantly different between the two groups (median, interquartile range; 11, 9–11 vs. 11, 9–11, P = 0.887). The percentage of patients with objective hyposmia (CC-SIT ≤ 10) was also not significantly different (47.4% vs. 40%,P = 0.762). OD in COVID-19 was normalized after 2 months of olfactory training in 70% of patients even after 3 months of olfactory impairment.
Conclusion
Although subjective olfactory function is significantly decreased in the OD group, the objective olfactory function was not significantly different. Moreover, olfactory training is effective in COVID-19 patients with OD.

Keyword

COVID-19; SARS-CoV-2; Olfaction Disorders

Figure

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  Fig. 1 Time from the onset of general or rhinologic symptoms to the onset of olfactory dysfunction.

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  Fig. 2 Changes of subjective and objective olfactory function after 2 months of olfactory training.sQOD-NS = short version of Questionnaire of Olfactory Disorders-negative statements, QOD-VAS = Questionnaire of Olfactory Disorders-visual analog scale, CC-SIT = Cross-Cultural Smell Identification Test, OD = olfactory dysfunction, OT = olfactory training.aIndependent t-test; bFisher's exact test.

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