Verification of azurocidin expression in the GCF samples. Azurocidin expression was confirmed in the GCF samples used for proteomic analysis by western blot (A) and the ELISA assay (B). (C) Azurocidin expression was further confirmed by ELISA in 156 individual GCF samples: 31 healthy individuals (N), 36 chronic gingivitis (GV), 59 moderate periodontitis (MP), and 30 severe chronic periodontitis (SP) patients (Additional files 2). All subjects were non-smokers and had no other disease indications or other conditions, e.g., diabetes, arteriosclerosis, hepatitis, AIDS, hypertension or pregnancy. Black diamond, Individuals; -, Average; ---, Cutoff. After the cutoff was set at 50 pg/ml, the sensitivity and specificity of azurocidin for the periodontitis patients were calculated (Table 4).