ROC analysis of logistic regression models (Figure 1 and Table 1) indicated that biomarkers have good potential to increase the accuracy that a plain questionnaire offers for identification of undiagnosed periodontitis patients: aMMP-8 AUC (95% CI) = 0.834 (0.761–0.906), total MMP-8 = 0.800 (0.722–0.878), active MMP-9 = 0.787 (0.704–0.870), total MMP-9 = 0.767 (0.680–0.855) and calprotectin = 0.773 (0.687–0.858) adjunct with the questionnaire vs. plain questionnaire = 0.764 (0.676–0.851). This evidence concerns the gene MMP8 and periodontitis.