Relationship between disease severity and serum IL-6 levels in COVID-19 anosmia

Abstract

Background An association between IL-6 levels and cytokine storm syndrome in COVID-19 patients has been suggested. Cases with higher IL-6 levels have more rapid progression and a higher complication rate. On the other hand, COVID-19 cases with anosmia have a milder course of the disease. Objective We aimed to investigate whether there is a relationship between serum IL-6 levels and presence of anosmia in COVID-19 patients. Methods Patients with a confirmed diagnosis of COVID-19 based on laboratory (PCR) were stratified into two groups based on presence of olfactory dysfunction (OD). In all cases with and without anosmia; psychophysical test (Sniffin' Sticks test) and a survey on olfactory symptoms were obtained. Threshold (t) – discrimination (d) – identification (i), and total (TDI) scores reflecting olfactory function were calculated. Clinical symptoms, serum IL-6 levels, other laboratory parameters, and chest computed tomography (CT) findings were recorded. Results A total of 59 patients were included, comprising 23 patients with anosmia and 36 patients without OD based on TDI scores. Patients with anosmia (41.39 ± 15.04) were significantly younger compared to cases without anosmia (52.19 ± 18.50). There was no significant difference between the groups in terms of comorbidities, smoking history, and symptoms including nasal congestion and rhinorrhea. Although serum IL-6 levels of all patients were above normal values (7 pg/mL), patients with anosmia had significantly lower serum IL-6 levels (16.72 ± 14.28 pg/ml) compared to patients without OD (60.95 ± 89.33 pg/ml) (p = 0.026). Conclusion Patients with COVID-19 related anosmia tend to have significantly lower serum levels of IL-6 compared to patients without OD, and the lower IL-6 levels is related to milder course of the disease. With the effect of low cytokine storm and IL-6 level, it may be said that anosmic cases have a milder disease in COVID-19.

The temporal course of COVID-19 anosmia and relation to other clinical symptoms

“…Nasal obstruction-related loss of smell is very common in viral infections; however, anosmia associated with COVID-19 is not commonly accompanied by nasal obstruction/congestion [6,14,21]. Similarly, in our study, the association of olfactory dysfunction with nasal congestion was found to be low with a ratio of 18.2%.…”

“…One plausible mechanism is high viral load in nasal mucosa with secondary inflammation which may result in direct injury to olfactory epithelium [13]. Another plausible mechanism involves angiotensin converting enzyme 2 (ACE2) receptors [14]. The olfactory epithelium has been found to express ACE2 and TMPRSS2, which may enable SARS-CoV-2 to invade the olfactory mucosa and olfactory bulb, and result in subsequent dysfunction [14][15][16].…”

“…Another plausible mechanism involves angiotensin converting enzyme 2 (ACE2) receptors [14]. The olfactory epithelium has been found to express ACE2 and TMPRSS2, which may enable SARS-CoV-2 to invade the olfactory mucosa and olfactory bulb, and result in subsequent dysfunction [14][15][16]. However, ACE2 expression is mainly seen in non-neuronal cell types like sustentacular, Bowman's gland, and microvillar cell, favoring indirect mechanisms of injury [17].…”

COVID-19 and chronic fatigue syndrome: Is the worst yet to come?

“…The most common symptoms of patients with COVID-19 are fever, cough, shortness of breath, and myalgia/fatigue [1] . Anosmia (loss of smell) and dysgeusia (altered sensation of taste) have been reported in 33–80% of patients with COVID-19 [2] . SARS-CoV-2 is mainly transmitted human-to-human through close contact, respiratory droplets, fomites, and contaminated surfaces [1] .…”

Return to Former Activities of Daily Living for Cardiovascular Patients in COVID-19

“…The coronavirus disease 2019 (COVID- 19), which started to spread from the wet animal market in the state of Wuhan in China at the end of 2019, was declared as a pandemic by the World Health Organization in March 2020 [1]. This is the third outbreak by coronaviruses in the 21st century.…”