comparison and agreement among various case definitions of periodontitis: a secondary data analysis

background and aims. a plethora of definitions has been used for periodontitis for epidemiological studies. the aim of this cross-sectional study was to assess the impact of different case definitions on the prevalence of periodontitis and to find the level of agreement among them. materials and methods. periodontal records of 300 subjects were randomly selected from the database of oral health center, international medical university. the prevalence of periodontitis was determined using six different case definitions of i, ii, iii, iv, va and vb previously used in various studies. the definition va proposed by cdc periodontal disease surveillance workgroup was adopted as the gold standard to calculate sensitivity and specificity. results. there were large variations in the prevalence of periodontitis based on different definitions, ranging from 28% to 76.7%. there was good agreement between definitions iii and vb (0.901) and definitions ii and iii (0.713). definition ii had the highest agreement with the gold standard (va) among all the definitions. excluding definition i, all had a high specificity to the gold standard. conclusion. the prevalence of periodontitis is greatly influenced by the choice of the case definition. prevalence rates with definition ii could be more accurate if the true prevalence is determined by definition va