title: Biomarkers of renal function, which and when?
abstract: OBJECTIVE
  Acute kidney injury (AKI) and chronic kidney disease (CKD) are conditions that substantially increase morbidity and mortality. Although novel biomarkers are being used in practice, the diagnosis of AKI and CKD is still made with surrogate markers of GFR, such as serum creatinine (SCr), urine output and creatinine based estimating equations. SCr is limited as a marker of kidney dysfunction in both settings and may be inaccurate in several situations, such as in patients with low muscle mass or with fluid overload. New biomarkers have the potential to identify earlier patients with AKI and CKD and in the future potentially intervene to modify outcomes.
  
  
  RESULTS
  In particular KIM-1 and NGAL are considered excellent biomarkers in urine and plasma for the early prediction of AKI; however cycle arrest biomarkers have emerged as novel markers for risk stratification of AKI. Urine TIMP-2 and IGFBP7 performed better than any other biomarkers reported to date for predicting the development of moderate or severe AKI. Biomarker combinations are required to increase diagnostic accuracy in an acute setting. NGAL, cystatin C, and FGF-23 are promising and accurate biomarkers for CKD detection. Equations combining cystatin C and SCr perform better than the equations using either cystatin C or SCr alone, especially in situations where CKD needs to be confirmed. Combining creatinine, cystatin C and urine albumin to creatinine ratio improves risk stratification for kidney disease progression and mortality.
  
  
  CONCLUSIONS
  Recent advances in molecular biology have resulted in promising biomarkers for AKI and CKD diagnoses; however more research is necessary to implement them successfully into clinical practice in order to facilitate early diagnosis, guide interventions and monitor disease progression. The following review describes the most important biomarkers studied in kidney disease and will discuss the use and the value of these biomarkers in different clinical settings.
authors.affiliation: Division of Nephrology, Department of Medicine, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Wasung
authors.affiliation: Department of Medicine, Division of Intensive Care Medicine, and the Division of Nephrology, Washington, DC, Veterans Affairs Medical Center, and the Department of Anesthesiology and Critical Care Medicine, George Washington University.
authors.forename: Lakhmir S
authors.initials: LS
authors.lastname: Chawla
authors.affiliation: Division of Nephrology, Department of Medicine, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico. Electronic address: madero.magdalena@gmail.com.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Madero
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000652:urine; D000209:Acute-Phase Proteins / Q000652:urine; D015415:Biomarkers / Q000097:blood / Q000652:urine; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood; D018450:Disease Progression; D042241:Early Diagnosis; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000652:urine; D005919:Glomerular Filtration Rate; D000072596:Hepatitis A Virus Cellular Receptor 1; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000652:urine; D007668:Kidney / Q000378:metabolism* / Q000473:pathology; D000071068:Lipocalin-2; D054834:Lipocalins / Q000097:blood* / Q000652:urine; D008562:Membrane Glycoproteins / Q000097:blood* / Q000652:urine; D011518:Proto-Oncogene Proteins / Q000097:blood* / Q000652:urine; D011991:Receptors, Virus / Q000097:blood*; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000652:urine; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000652:urine
chemical_list: D000209:Acute-Phase Proteins; D015415:Biomarkers; D055316:Cystatin C; C000717427:FGF23 protein, human; C491143:HAVCR1 protein, human; D000072596:Hepatitis A Virus Cellular Receptor 1; D018969:Insulin-Like Growth Factor Binding Proteins; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D011991:Receptors, Virus; C560823:TIMP2 protein, human; C102529:insulin-like growth factor binding protein-related protein 1; D019716:Tissue Inhibitor of Metalloproteinase-2; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D003404:Creatinine
keywords: Acute kidney injury; Biomarkers; Chronic kidney disease