Thereafter, seven hypothetical negative studies were filled through the “trim and fill” approach, but RASSF1A promoter methylation was found to be significantly associated with HCC risk in the pooled analyses (OR = 15.71, 95% CI = 7.40–33.36, P < 0.001) (Additional file 1: Figure S2D). The gene discussed is RASSF1; the disease is hepatocellular carcinoma.