For six genes reported in at least three studies between HCC tumor serums and normal serums (Table 3), no evidence of statistical heterogeneity was observed for four genes, including RASSF1A (I2 = 0%), p16 (I2 = 0%), CDH1 (I2 = 0%), RUNX3 (I2 = 0%), GSTP1 (I2 = 0%) and WIF1 (I2 = 0%). This evidence concerns the gene CDKN2A and hepatocellular carcinoma.