Serum and salivary interleukin-4 levels in patients with oral lichen planus: A systematic review and meta-analysis

Objective. Cytokines have an important role in keratinocyte immune damage and can act in the pathogenesis of different cutaneous diseases. Accordingly, in the literature, interleukin 4 (IL-4) concentration has been previously investigated in patients affected by oral lichen planus (OLP). Study design. The present meta-analysis evaluated the serum and salivary levels of IL-4 in connection with several OLP variants. The search was performed from 1995 in Cochrane Library and 1983 in Scopus, PubMed, and Web of Science to September 2018. The quality of the studies included in the meta-analysis was assessed using the Newcastle-Ottawa Scale assessment. The analyses were done by Review Manager 5.3 using mean difference (MD) and 95% confidence intervals (CIs). Results. Out of 108 studies retrieved in the databases, only 10 were included and analyzed in quantitative synthesis. The pooled MD of the serum and salivary IL-4 levels in OLP patients compared with the controls was 6.36 picograms/milliliter (pg/mL) (95% CI: 1.47, 11.24; P = .01) and 2.67 pg/mL (95% CI: 2.66, 2.68; P < .00001), respectively. In addition, the pooled MD of serum and salivary IL-4 level was 1.30 pg/mL (95% CI: -0.35, 2.95; P = .12) and 1.83 pg/mL (95% CI: 0.26, 3.40; P = .02), respectively, in patients with erosive, erythematous, bullous, and ulcerative variants of OLP compared with patients with reticular OLP. Conclusions. This meta-analysis found that OLP patients present elevated serum and salivary IL-4 levels, thus indicating that IL-4 may represent a potential salivary biomarker for the disease. By contrast, clinicians must be aware that even other factors (e.g., secondary infection) may influence its concentration.