CST3 and hydrops fetalis: IL-34 levels were also significantly higher in patients with cystatin C ≥ 1.550 (median) compared to those with cystatin C < 1.550 (135.26 ± 10.38 pg/mL vs. 98.00 ± 7.75 pg/mL, p < 0.0001) among patients with HF (Fig. 1B).