Most population surveys suggest that approximately half of HF patients suffer HFREF, in contrast to the 12% detected in REFER, and in this sensitivity scenario the dominant cost-effective strategy is the reduced NT-proBNP cut-off for referral for echocardiography of 125 pg/ml rather than the NICE level of 400 pg/ml. The gene discussed is NPPB; the disease is hydrops fetalis.