Table 1.

Diagnosis and staging criteria for AKI of RIFLE, AKIN, KDIGO, and CK definitions based on serum creatinine

Classification	Definition for AKI	Stage	Serum Creatinine Criteria for AKI Staginga
RIFLE	Increase in SCr ≥50% within 7 d	Risk	To ≥1.5 times baseline
		Injury	To ≥2 times baseline
		Failure	To ≥3 times baseline or ≥0.5 mg/dl increase to at least 4.0 mg/dl
AKIN	Increase in SCr ≥0.3 mg/dl or ≥50% within 48 h	1	Increase of ≥0.3 mg/dl or to 1.5–1.9 times baseline
		2	To 2–2.9 times baseline
		3	To ≥3 times baseline or ≥0.5 mg/dl increase to at least 4.0 mg/dl or initiation of RRT
KDIGO	Increase in SCr ≥0.3 mg/dl within 48 h or ≥50% within 7 d	1	Increase in SCr ≥0.3 mg/dl within 48 h or to 1.5–1.9 times baseline
		2	To 2.0–2.9 times baseline
		3	To 3.0 times baseline or to at least 4.0 mg/dl or initiation of RRT
CK	Increase in SCr ≥0.3 mg/dl within 24 h or ≥0.5 mg/dl within 48 h	1	Increase in SCr ≥0.3 mg/dl within 24 h or ≥0.5 mg/dl within 48 h
		2	Increase in SCr ≥0.5 mg/dl within 24 h or ≥1.0 mg/dl within 48 h
		3	Increase in SCr ≥1.0 mg/dl within 24 h or ≥1.5 mg/dl within 48 h

For patients meeting diagnosis criteria for AKI according to RIFLE, AKIN, or KDIGO, the stages based on percentage increase were determined by the ratio of peak SCr value obtained during hospitalization to baseline. RIFLE, Risk Injury Failure Loss ESRD; AKIN, Acute Kidney Injury Network; KDIGO, Kidney Disease Improving Global Outcomes; CK, creatinine kinetics; SCr, serum creatinine; RRT, renal replacement therapy.

^aUrine output was not used, because records of hourly urine output were not available in the majority of patients.