CCRL2 and periodontitis: Additionally, the AUCs of ACSL5, NLRP12, CCRL2, and CEACAM3 in the periodontitis training dataset were 0.771, 0.819, 0.708 and 0.785, respectively, which also suggested the diagnostic values of 4 hub genes on periodontitis were strong (Additional file 4: Fig. S4).