Taste and smell disorders in COVID-19 patients: role of Interleukin-6

The rapid recovery of smell and/or taste functions in COVID-19 patients could be attributed to a decrease in Interleukin-6 levels rather than central nervous system ischemic injury or viral damage to neuronal cells. To correlate Interleukin-6 levels in COVID-19 patients with olfactory and/or gustatory dysfunctions and to investigate the role of IL-6 in the onset of these disorders. This observational study investigated 67 COVID-19 patients with taste and/or smell disorders, who did not require intensive care admission, admitted at COVID Hospital of Policlinico of Bari from March to May 2020. Interleukin-6 was assayed to COVID-19 patients with taste and/or smell disturbances at the time of admission and at the time of swab negativization. At the same time, patients have been given a specific survey to evaluate the severity of taste and/or smell disturbances. Of 125 patients with smell and/or taste dysfunctions at onset of disease, 67 fulfilled the inclusion criteria, while 58 were excluded because 35 of them required intensive care admission, 5 were unable to answer, 5 deceased, 7 had finished chemotherapy recently and 5 refused. The evaluation of taste and/or smell disorders was carried out using a survey performed at the time of admission and at the time of swab negativization. Sino-nasal outcome test 22 (SNOT-22) was used as a reference for olfactory function assessment and Taste and Smell Questionnaire Section of the US NHANES 2011–2014 protocol (CDC 2013b) was used as reference for gustatory function assessment. A venous blood sample was taken for each patient to measure IL-6 levels upon entry and at swab negativization. Interleukin-6 levels in COVID-19 patients in relation with olfactory and/or gustatory disorders from the time of their admission to the time of swab negativization. Statistically significant correlations were obtained between the decrease of Interleukin-6 levels and the improvement of smell (p value<0,05) and taste (p=0,047) functions at swab negativization. The acquired results demonstrate the key role of Interleukin-6 in the pathogenesis of chemosensitive disorders in COVID-19 patients.