Blood NT-proBNP is the gold standard biomarker for HF diagnosis and monitoring, and high levels of NT-proBNP in blood have been associated with cardiac (e.g. ejection fraction), renal (e.g. serum creatinine), and laboratory parameters (e.g. serum potassium and hemoglobin)44,45, as well as a higher NYHA class46. This evidence concerns the gene NPPB and hydrops fetalis.