Objectives: To evaluate the relationship between late olfactory function in post-COVID-19 patients and serological inflammatory markers in the acute phase.
Methods: Cross-sectional, analytical and observational study. A number of 123 patients with a history of hospitalization by COVID-19 were recruited. Olfactory dysfunction (OC) was evaluated using the Connecticut Chemosensory Clinical Research Center (CCCRC) test, and data from the medical records were reviewed regarding serological markers of acute systemic inflammation – lymphocytes, lactate dehydrogenase (LDH), ferritin, C-reactive protein (PCR) and D-dimmer.
Results: The mean interval between onset of COVID symptoms and the CCCRC test was 172 days. There was a significant association between age over 60 years and CCCRC (p=0.03). It was verified the presence of a relationship with statistical significance between increased LDH values and worse score in the CCCRC (p=0.049). However, the correlation found was weak (r=0.19). The other markers evaluated did not present statistical significance when crossed with CRF. The result was similar in the cross between serum inflammatory markers and degree of severity of OD.
Discussion: In the presence of the pandemic by COVID-19, OD has become a complaint of high prevalence, leading to an important loss of quality of life for patients. According to Cazzola et al., the cells that express the angiotensin-2-converter enzyme – including the nasal epithelial cells – are the target of attack for SARS-CoV-2. The attack on cells triggers the appearance of an inflammatory storm. The correlation between the severity of the infection and the degree and duration of OD is controversial. Although the relationship between worse olfactory score in the acute phase with exacerbated systemic inflammation and worse clinical outcomes has been reported, some studies have shown contradictory results. Mangia et al. demonstrated worse olfactory score in the acute phase in patients with worse clinical outcomes. However, Vaira et al. found no correlation between OD and poor prognosis. Similarly, Izquierdo-Dominguez et al. observed that the frequency of OD was more prominent in outpatient cases without pulmonary involvement. Regarding systemic inflammatory markers, studies have observed a relationship between elevated serum levels with the most severe forms of COVID-19, due to cytokine storm. The relationship of serum biomarkers with the highest severity of infection has also been constant in research. Chen et al. found higher CRP level in the severe group, but without statistical significance. Meta-analysis conducted by Zeng et al. demonstrated higher serum ferritin levels in patients with severe COVID-19. Izquierdo-Dominguez et al. observed in multivariate analysis that hospitalization and increase in serum CRP levels were associated with better olfactory. Analyzing the relationship between serological inflammatory markers in the serological phase and OD, Vaira et al. described that the correlations between olfactory and Serum levels of inflammatory markers were weak and not significant. In the present study, despite the statistically significant association between LDH levels and the CCCRC, the estimated correlation coefficient is low, corresponding to a weak correlation. In crossing the LDH with the degrees of severity of the CCCRC, no statistical significance was found. On the other than the other serum markers evaluated, the other serum markers did not present a significant correlation with the psychophysical test and were not associated with the degrees of severity of the CCCRC. The results found in this study are compatible with vaira et al. and Izquierdo-Dominguez et al., which may suggest little influence of systemic inflammation on the nasal mucosa.
Conclusion: The present study suggests that there is no relationship between high levels of serum markers – CRP, lymphocytes, D-dummy and ferritin – with worse late olfactory function in the post-COVID-19 patient. A low-grade correlation is observed between LDH and CCCRC; however, this association was not relevant when correlated with the degree of severity of OD.
Keywords: Coronavirus; Olfactory dysfunction; Inflammatory markers.
