To avoid prejudice against a small sample size, we performed an ELISA assay of azurocidin with 31 N, 36 gingivitis (GV), 59 MP, and 30 severe periodontitis (SP) patients (Additional files 2), and the average levels of azurocidin in each sample were 40.8 pg/ml, 136.6 pg/ml, 118.3 pg/ml, and 85.3 pg/ml, respectively. This evidence concerns the gene AZU1 and periodontitis.