Figure 2 summarizes the obtained meta-analysis results. The pooled analysis that assessed OPG levels in adult HF patients vs. control subjects showed an overall MD of 2.490 (95% CI 0.531, 4.449). Considerable heterogeneity was reported with an I2 = 99.93% and a p-value < 0.001. The gene discussed is TNFRSF11B; the disease is hydrops fetalis.