Creatinine.
OBJECTIVE
To summarize the history and current findings for creatinine as a renal biomarker and try to predict its future, looking at new biomarkers for kidneys (neutrophil gelatinase-associated lipocalin and cystatin C) and comparing current development to other diseases (troponins and procalcitonin).


RESULTS
In general, biomarkers are used for diagnosis, severity classification, outcome prediction, and most importantly, outcome modification. Creatinine can be used for the first three (except for outcome modification). Multiple clinical studies have shown that new renal biomarkers, especially neutrophil gelatinase-associated lipocalin and cystatin C, can diagnose acute kidney injury more rapidly and accurately, have a better relationship with disease severity, and predict outcome of patients with acute kidney injury more accurately, than creatinine. However, to prove the true superiority of the new renal biomarkers to creatinine, more clinical studies will be required. Such studies include interventional ones that can improve outcome (especially mortality) of patients with acute kidney injury and ones showing relationship of the markers with beneficial effects of specific interventions.


CONCLUSIONS
Unless enough evidence accumulates, considering the history, familiarity, and recent findings related to outcome, creatinine will continue to be used and dominate in clinical practice.
Uchino
Shigehiko
S
Department of Anesthesiology, Intensive Care Unit, Jikei University School of Medicine, Tokyo, Japan. s.uchino@jikei.ac.jp
D058186:Acute Kidney Injury / Q000097:blood* / Q000175:diagnosis* / Q000209:etiology; D000209:Acute-Phase Proteins; D015415:Biomarkers; D001774:Blood Chemical Analysis; D002116:Calcitonin / Q000097:blood; D015740:Calcitonin Gene-Related Peptide; D006348:Cardiac Surgical Procedures / Q000009:adverse effects; D002315:Cardiopulmonary Bypass; D003404:Creatinine / Q000097:blood* / Q000378:metabolism; D003422:Critical Care; D055316:Cystatin C / Q000097:blood; D006801:Humans; D007362:Intensive Care Units; D000071068:Lipocalin-2; D054834:Lipocalins / Q000097:blood; D063305:Organ Dysfunction Scores; D011183:Postoperative Complications / Q000175:diagnosis; D011498:Protein Precursors / Q000097:blood; D011518:Proto-Oncogene Proteins / Q000097:blood; D012680:Sensitivity and Specificity; D014336:Troponin / Q000097:blood
D000209:Acute-Phase Proteins; D015415:Biomarkers; C000606589:CALCA protein, human; D055316:Cystatin C; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D011498:Protein Precursors; D011518:Proto-Oncogene Proteins; D014336:Troponin; D002116:Calcitonin; D003404:Creatinine; D015740:Calcitonin Gene-Related Peptide