Association between Interleukin-6 Promoter Polymorphism (-174 G/C), Serum Interleukin-6 Levels and Mortality in Severe Septic Patients

The association between interleukin (IL)-6 promoter polymorphism (-174 G/C), circulating IL-6 levels and mortality in septic patients has scarcely been addressed, and then only in studies of small sample size, and a direct association among them has not been previously reported. Therefore, the purpose of our study was to determine whether this association exists. An observational, prospective and multicenter study including severe septic patients was undertaken and serum IL-6 levels at severe sepsis diagnosis and IL-6 promoter polymorphism (-174 G/C) were determined. The end-point of the study was 30-day mortality. The study included 263 patients with the following genotypes of IL-6 promoter polymorphism (-174 G/C): 123 (46.8%) GG, 110 (41.8%) GC and 30 (11.4%) CC. CC homozygous patients showed lower sepsis-related organ failure assessment (SOFA) score, serum IL-6 levels and mortality at 30 days compared to those with other genotypes (GC or GG). On regression analysis, CC homozygous patients showed lower 30-day mortality than those with genotype GG (odds ratio = 0.21; 95% CI = 0.053 0.838; p = 0.03) or GC (hazard ratio = 0.28; 95% CI = 0.074 1.037; p = 0.06). The most important results of our study were that CC might be a favorable genotype in septic patients showing lower serum IL-6 levels and lower risk of death within 30 days.