The correlation of serum and gingival crevicular fluid cytokines in obese subjects

To investigate the correlation between the gingival crevicular fluid (GCF) levels of IL-6 and TNF-alpha with the levels in serum in obese patients.

Twenty-six obese adults (BMI > or = 30, age 33-74) provided serum and GCF samples. Smokers and uncontrolled diabetics (HbA1c > 8%) were excluded. Serum and GCF samples were analysed for IL-6 and TNF-alpha using commercially available ELISA kits. Within each subject GCF was collected from two healthy sites (n = 26 subjects) and two gingivitis sites, defined by bleeding on probing (n = 22 subjects). The levels of IL-6 and TNF-alpha in the GCF were compared and correlated with the levels found in serum using Spearman's correlation analysis. A Bland-Altman analysis was used to determine the level of agreement between serum and GCF samples.

IL-6 was more frequently detected than TNF-alpha. This was consistent in serum (100% vs 64%) and GCF samples from healthy (73% vs 52%) and gingivitis (95% vs 36%) sites. There were no significant correlations between the TNF-alpha in serum and GCF samples from healthy (r = 0.27, p = 0.22) and gingivitis (r = -0.19, p = 0.40) sites. In contrast, positive correlations were found for IL-6 between serum and GCF samples from healthy (r = 0.48, p = 0.03) and gingivitis (r = 0.79, p = 0.0001) sites. The correlation and agreement was strongest for IL-6 between serum and gingivitis GCF samples.

The results of this pilot study suggest a lack of correlation and poor agreement between serum and GCF samples in obese subjects. Studies examining the link between periodontitis and obesity should consider collecting both serum and GCF.