Recently, Luk et al.(77) recruited 39 adult patients with pre-existing CKD whopresented to the hospital with acute-on-chronic renal failure in stages I or Fof the RIFLE classification (excluding patients with anuria) and collected,within the first 24 hours of admission, urine samples to examine neutrophilgelatinase-associated lipocalin (NGAL) and the mRNA expressions of kidney injurymolecule-1, interleukin-18 (IL-18), alpha-1-microglobulin (α-1-M),sodium/hydrogen exchanger-3, beta-2 microglobulin andN-acetyl-β-D-glucosaminidase. Here, SLC9A3 is linked to chronic kidney disease.