NPPB and kidney failure: RBP4 levels were also correlated with markers of renal failure, specifically sCr (r = 0.224, p = 0.005) (Figure 3c), but they were not correlated with BNP (r = −0.005, p = 0.958) (Figure 3d) and ALB (r = 0.199, p = 0.057) levels (Figure 3e).