Challenges facing early detection of acute kidney injury in the critically ill

Table 1 Possible future modes of diagnosing acute kidney injury

AKI diagnosis	Timing	Staging	Examples
Injury biomarkers	Within 0-12 h of injury and every 3 to 6 h	Cutpoints of concentrations	Urinary NGAL, cystain C, IL-18, KIM-1, GGT, L-FABP, Plasma NGAL
Functional measurements	Any time following injury	Change from a baseline	4 h creatinine clearance, ARM urine output
Surrogates of function	12 h to 7 d post injury	Change from a baseline	Plasma creatinine, plasma cystatin C

NGAL: Neutrophil-gelatinase-associated-lipocalin; IL-18: Interleukin-18; KIM-1: Kidney injury molecule-1; GGT: γ-glutamyl-transpeptidase; L-FABP: Liver-fatty acid binding protein; ARM: Ambulatory renal monitor; AKI: Acute kidney injury.