Periodontal disease definition Kappa statistics Beck et al. [20] Machtei et al. [21] Lopez et al. [22] Page and Eke [23] Page and Eke [23] Borrell et al. [24] Hujoel et al. [19] 0.86 * 0.56* 0.88* 0.53* 0.55* 0.85* Beck et al. [20] 1 0.69* 0.88* 0.44* 0.67* 0.78* Machtei et al. [21]   1 0.67* 0.26* 0.98* 0.50* Lopez et al. [22]     1 0.45* 0.65* 0.80* Page and Eke [23]       1 0.25* 0.62* Page and Eke [23]         1 0.48* Borrell et al. [24]           1 * P-value < 0.05

Table 3: The agreement (kappa statistics) between different periodontal disease definitions.