Effect of the IL-6 promoter polymorphism -174 G/C on risk and outcome of pneumonia

Introduction

IL-6 is a pleiotropic cytokine expressed in many tissues. A polymorphism in the IL-6 gene, associated with differences in the IL-6 transcription rate, has been recently described [1]. The influence of genetic polymorphisms of IL-6 gene promoter -174 G/C on the severity of systemic inflammatory response syndrome associated with community-acquired pneumonia (CAP) was studied.

Methods

A prospective, multicentric case–control study in three university hospitals in Spain. In 852 consecutive patients who presented with CAP and 923 controls, using PCR-RFLP analysis, we analyzed the -174G/C single nucleotide polymorphism of the IL-6 gene. The pneumonia severity was assessed on the day of admission and stratified according to the PORT score and complications recorded such as respiratory failure, renal impairment, severe sepsis, shock and multiorgan failure. Outcomes evaluated were the duration of hospital stay, ICU admittance, and inhospital and 28-day mortality.

Results

See Table 1. The distribution of the G/C 174 genotype was similar in CAP patients and controls. The genotype distribution of the polymorphism was 45.07% for GG and 43.89% and 11.03% for GC and CC, respectively. In patients who were admitted with CAP, no significant differences were observed compared with progression between groups.

Table 1

Multivariate analysis (which included genotype, age, sex, and classical risk factors for CAP) identified the C/C genotype as the only independent predictor of renal failure.

Conclusion

Our findings show that the 174G/C polymorphism is not associated with risk and outcome of CAP in the Spanish white Caucasian population.