NPPB and congestive heart failure: But a subsequent prospective cohort study showed that in elderly patients with chronic heart failure, blood RBP4 levels were negatively correlated with left ventricular ejection fraction (LVEF) and positively correlated with NT-proBNP, and that serum RBP4 levels increased with decreasing cardiac function (Li et al., 2020; Table 1), In addition, the results of a 60-month follow-up suggested that blood RBP4 levels were positively correlated with adverse events in patients with chronic heart failure.