Persistent olfactory alterations in Post-Covid-19 condition. A systematic review and cross-sectional study on persistent olfaction alterations in Post-Covid-19 condition in the OSI Enkarterri-Ezkerraldea-Cruces

Abstract

[EN] INTRODUCTION: The phenotype of Post-Covid-19 Condition (PC19C) has not precisely been described yet. Olfaction alteration is clearly part of the acute phase of the infection, but it remains unclear if it is part of the defining features of PC19C. PRIMARY OBJECTIVES: To determine whether PC19C patients suffer from persistent olfactory alterations more frequently than the healthy population, comparing it to current literature. As well as, to objectify this damage with a validated and objective measurement tool such as the B-SIT (brief smell identification test). MATERIAL AND METHODS: A systematic review and a cross-sectional study were performed. The databases used for the systematic review were Pubmed and SpringerLink. In total 39 papers were included in the review. For the cross-sectional study 40 PC19C patients and 40 controls that had not been infected by Sars-CoV-2 were tested (n=80). First, they filled out a questionnaire to rule out other reasons for olfaction alteration, and then, they realized the B-SIT. The results of the two groups were statistically compared by GraphPad Prism 8 and SSPS. For significance testing, the alpha level was set to 0.05 (α=0.05). RESULTS: There were no significant differences in the smelling performance of PC19C patients and the general population. Although hospitalized patients' results were significantly lower (p = 0.04). Literature supports our findings and presents other possible risk factors associated with long-lasting olfaction alteration, such as being a female, smoking, or younger age. CONCLUSIONS: The prevalence of olfaction alteration in PC19C patients is not higher than in the general population. Hospitalized patients have higher smelling difficulties than non-hospitalized patients and the general population. Neuroplasticity is a possible explanation for olfaction recovery, as olfaction training treatments' success may entail.