In the case of health vs gingivitis groups comparison, the ROC and corresponding AUC statistics for the selected markers and combinations thereof are presented in Fig. 2A. The plotted ROC curves showed a good predictor value of the MMP-9/TIMP-1 ratio, (MMP-8 + MMP-9)/TIMP-1 ratio, and MMP-3 for differentiation of gingivitis versus health conditions (AUC ≥ 0.80). The gene discussed is TIMP1; the disease is gingivitis.