Taste and Smell Disorders in COVID-19 Patients: Role of Interleukin-6

Abstract

The rapid recovery of smell and 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 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 or smell disorders or both, who did not require intensive care admission, admitted at COVID Hospital of Policlinico of Bari from March to May 2020. Interleukin-6 was assayed in COVID-19 patients with taste 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 smell disturbances. Of 125 patients with smell 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 died, 7 had finished chemotherapy recently, and 5 refused to participate. The evaluation of taste and smell disorders was carried out using a survey performed at the time of admission and at the time of swab negativization. Sinonasal 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 to olfactory or gustatory disorders were correlated 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.

New Insights in Laboratory Testing for COVID-19 Patients: Looking for the Role and Predictive Value of Human epididymis secretory protein 4 (HE4) and the Innate Immunity of the Oral Cavity and Respiratory Tract

“…COVID-19 infection is a systemic disease that recognizes the throat and nose as a gateway, in which the virus finds a welcoming environment for replication. The viral replication occurs in the upper respiratory tract and then spreads throughout the body with devastating consequences [10,11].…”

“…Elevated levels of IL-6 were significantly related to taste and smell disorders [11] and to severe clinical manifestations in critically ill patients, in intensive care with respiratory failure and with poor prognosis [32].…”

The Coronavirus Disease-19 Infection and the Oral Mucosa

“…The oral mucosa could be stimulated by speaking, coughing, and sneezing and viral particles have the ability to become aerosolized; they can stay in the air for 3 or more hours and may spread to contaminate multiple surfaces in the surrounding area [4]. As a consequence, the SARS-CoV-2 became able to interfere with both respiratory and oral environment, also determining temporary (and perhaps permanent) damages of central nervous system [5], [6].…”

The human coronaviruses (HCoVs) and the molecular mechanisms of SARS-CoV-2 infection

“…The activation of the coagulation system and the dysregulation of the ACE2 also lead to endothelial damage thus causing an increase in the possibility of formation of clots and microthrombi/thrombi (such as pulmonary embolism, deep vein thrombosis, large vessel stroke, arterial and venous thromboembolism); increase the risk of lung damage with edema, diffused alveolar destruction (DAD), severe hypoxemia; and can evolve into acute respiratory distress syndrome (ARDS) and afterwards multi organ failure (MOF) more frequent and lasting than pulmonary ones. This can be linked precisely to the imbalance of the intestine/lung axis, or from bacterial dysbiosis, or to an ischemic damage of the central nervous system, but also from interleukin-6 which can also be facilitated by nasopharyngeal dysbiosis [71][72][73][74][75]. The most common skin manifestations associated with SARS-CoV-2 infection include a maculo-papular or papulo-vesicular rash, urticaria lesions, and livedo reticularis.…”