Utility of IL-6 in the diagnosis, treatment and prognosis of COVID-19 patients: A longitudinal study

Introduction Covid-19 has caused devastating effects worldwide ever since its origin in December, 2019. Till date, there is no definitive treatment for it. Deaths due to Covid-19 has largely been attributed to cytokine storm and organ dysfunctions, mainly ARDS. Therefore, the focus has been on using inflammatory markers as a marker of severity of the disease. IL-6 is one such marker which has been increasingly used in the management of Covid-19. We conducted a longitudinal study to investigate the role of IL-6 in diagnosis, treatment and prognosis of Covid-19 related cytokine storm. Methodology Patients with Covid-19, who were admitted at AIIMS Rishikesh from March to December, 2020 were included in the study. Patients with no baseline IL-6 value at admission and for whom clinical data was not available were excluded. Clinical and laboratory data of these patients were collected from the e-hospital portal and entered in excel sheet. Correlation was seen with other inflammatory markers and outcomes were assessed using MS Excel 2010 and SPSS software. Results At total of 131 patients were included in the study. Majority were males (74.8%), mean age of the subjects being 55.03 + 13.57 years, with a mean duration from symptom onset being 6.69 + 6.3 days. Most of them belonged to the WHO severe category (82.4%), with 46.56% having severe hypoxia at presentation and 61.8% of them having some comorbidity-diabetes mellitus being the commonest. Spearman Rank Correlation coefficient of IL-6 with D-dimer was 0.203, with LDH was -0.005, with Ferritin was 0.3, and with Uric acid was 0.123. 11 patients received Tocilizumab at a mean duration from symptom onset of 18.09 days, and 100% mortality was observed. Deaths were reported more in the group with IL-6 more than 40pg/ml (57.1% vs 40.2%,p=0.06). Similarly, ICU admissions and ventilator requirement were reported more in the IL-6 more than 40pg/ml group (95.9% vs 91.4%,p=0.32 and 55.1% vs 37.8%,p=0.05). Conclusion The study showed that IL-6 can be used as a possible thrombotic cytokine marker. Higher values of IL-6 ( > 40pg/ml) are associated with more deaths, ICU admissions and ventilator requirement.