Disclosed is a system, a kit, a use and an in vitro method for assessing whether a human patient suffering from periodontitis has mild periodontitis or advanced periodontitis. The system and method are based on the insight to apply a clustering technique to a reference set of patient data, and then further discriminating the sets of bio markers to be applied. The clusters are determined on the basis of the biomarkers Hepatocyte Growth Factor (HGF), Matrix metalloproteinase 8 (MMP8), and Matrix metalloproteinase 9 (MMP9). The actual classification of the patient is done on the basis of the measurement of the concentrations of either of two sets of biomarkers. For one cluster these are Interleukin-1β (IL1β), Interleukin-6 (IL6), and Collagen Telopeptide. For the other cluster, these are HGF and metallopeptidase inhibitor 1 (TIMP1).