A plethora of case definitions of periodontitis were retrieved (as shown in Supplementary Tables 5, 6) as well as variability in the used CRP and hs-CRP methods (i.e., immunoturbidimetry, nephelometry, ELISA, CLIA, RIA, Cardiac-specific claim, latex agglutination method and spectrophotometer) (Supplementary Tables 5, 6). This evidence concerns the gene CRP and periodontitis.