The relationship between levels of salivary and serum interleukin-6 and oral lichen planus: A systematic review and meta-analysis.

BACKGROUND: The relationship between levels of salivary and serum interleukin (IL)-6 and oral lichen planus (OLP) is not understood fully. The authors conducted a systematic review and meta-analysis to compare levels of salivary and serum IL-6 among people with OLP and healthy control participants. METHODS: The authors searched the literature for studies whose investigators had evaluated the relationships between IL-6 and OLP before treatment. The authors used meta-analysis to compare the standardized mean differences (SMD) of the levels of salivary and serum IL-6 between people who had OLP and people who did not have OLP and between patients with erosive OLP and patients with nonerosive OLP. RESULTS: The results of separate meta-analyses, which included 5 studies each, indicated that the levels of salivary and serum IL-6 were significantly higher among patients with OLP than among healthy control participants (SMD, 2.35; 95% confidence interval [CI], 0.50 to 4.19; P = .01; and SMD, 2.03; 95% CI, 0.74 to 3.33; P = .002; respectively). The results of a meta-analysis of 4 studies indicated that the levels of IL-6 were not significantly different between patients with erosive OLP and patients with nonerosive OLP (SMD, 1.37; 95% CI, -0.26 to 3.00; P = .10). There was significant heterogeneity among the studies (P < .00001). CONCLUSIONS: Through the results of this meta-analysis, the authors found significant differences in the levels of IL-6 in saliva and serum between patients with OLP and healthy control participants. The authors found no differences in the levels of serum IL-6 between patients with erosive OLP and patients with nonerosive OLP. These results should be considered with caution because there was a high degree of heterogeneity among studies. PRACTICAL IMPLICATIONS: Levels of IL-6 in saliva and serum may be potential biomarkers for OLP. However, additional research is needed to confirm findings of this meta-analysis.