Nuances in COVID-19-Related Olfactory Dysfunction: An Observational Study

ABSTRACT

Introduction: Almost 30% of olfactory dysfunction (OD) arises after a viral infection with increased incidence due to COVID-19. Hypothesized SARS-CoV-2 viral attachment to the olfactory epithelium differs from the traditional postviral OD (PVOD) mechanism. Hence, manifestations of OD may differ between the two etiologies. This study evaluates the difference in smell perception between post-COVID-19 OD and postviral or idiopathic etiologies. Method(s) This observational study, approved by the institutional review board, was conducted between September 2020 and January 2022 in adult patients with more than 6 months nontraumatic OD with no perceived improvement in smell even after 3 months of conservative treatment. OD in these patients was categorized as COVID-19 or non-COVID-19 related. Demographics, duration of OD, and Brief Smell Identification Test (B-SIT) scores were analyzed. Continuous variables were compared by t test, while categorical variables were compared by chi2 test using SPSS 27 (IBM Corp). Result(s) Of the 26 patients included in the study, 42.3% reported persistent OD following COVID-19 infection, while 57.7% had non-COVID-19-related OD. The mean B-SIT score in post-COVID-19 OD was 6.81+/-2.15 compared with 3.87+/-2.2 in the non-COVID-19 OD group, with the difference being statistically significant at 3.40 (P=.001). While race and gender ratios were similar between the groups, age (42 vs 54, P=.048) and duration of loss of smell (10 months vs 49 months, P<.001) had significant differences. Conclusion(s) This study shows that patients suffering from COVID-19-related OD may have normal scores on scratch and sniff smell tests, possibly because of the difference in the affected site of the olfactory pathway. Current hypotheses focus on olfactory epithelial damage in COVID-19 vs neuronal in PVOD. Differences seen in age and duration of smell loss between groups may be secondary to newfound worldwide attention to OD, while patients with OD etiologies predating COVID-19 may have newly sought treatment at this time. Olfactory threshold testing may be required for accurate assessment of post- COVID-19 OD. Larger studies are required to help delineate differences between these olfactory disturbance etiologies.