Although the correlation between BNP and NT-proBNP levels was statistically significant in CKD stages 1-5 (Fig. 2), it became weaker as CKD stage increased (CKD stages 1 and 2; r = 0.914, p < 0.0001; CKD stage 3; r = 0.865, p < 0.0001; CKD stage 4; r = 0.878, p < 0.0001; CKD stage 5; r = 0.786, p < 0.0001; CKD stage 5D; r = 0.691, p < 0.0001; CKD stage 1-5; r = 0.814, p < 0.0001). This evidence concerns the gene NPPB and chronic kidney disease.