Introduction: This is because the development of cytokine release syndrome (CRS) as the pathologic basis for the progression of severe Covid-19 disease is possible.

Material and Methods: A two-step selection process that involved first screening studies based on their titles and abstracts and then reading the full texts of those studies was carried out independently by the two reviewers. Studies were considered if they were RCTs, observational cohorts, or case-control in design, described two or more patients diagnosed with Covid19, and reported measures of cytokine levels (with a focus on IL-6). The use of standardized data extraction tables allowed for the duplication of the data extraction process. Data were taken from the text of the article, the tables, and the graphs.

Results: In all of the studies that were included, elevated IL-6 levels were found in Covid-19 patients. Numerous studies specifically found that patients with more severe (complicated) diseases had higher levels of IL-6 descriptions of other inflammatory markers, such as ferritin and IL2R. Six studies in total compared the levels of IL-6 in patients with complicated disease (those with ARDS, needing ICU admission, or having "severe" or "critical" presentations according to the Chinese New Coronavirus Pneumonia Prevention and Control Program score) and noncomplicated disease (those without the aforementioned criteria present).

Conclusion: In this systematic review and meta-analysis, we show that elevated serum IL-6 levels are associated with complicated Covid 19 disease and that these elevated IL-6 levels are also significantly associated with poor clinical outcomes. This implies that an excessive host immune response and autoimmune injury may be the result of an initial SARS-CoV2 infection that progresses to a complicated disease. These results underline the necessity of continuing, carefully designed clinical studies to clarify the function of immunomodulation, specifically IL-6 inhibition, in the treatment of severe Covid-19.