Table 1.

Incidence, diagnostic criteria, and time point of diagnosis of AKI by cohort. Categorical data are presented as the absolute number and percentage. Diagnosis of AKI was based on Kidney Disease Improving Global Outcomes (KDIGO) clinical practice guidelines ((1) an increase in serum creatinine of at least 0.3 mg/dL or an increase of 50% above baseline and/or (2) a decline in urine output to below 0.5 mL/kg/h for at least 6 h) [16]. Most patients diagnosed with AKI were affected by AKI stage 1 and were diagnosed 48 h after surgery. All patients suffering from AKI showed an increase in serum creatinine. Approximately 40% of AKI patients had persistent AKI lasting >48 h. AKI, acute kidney injury.

Acute Kidney Injury within 72 h after Cardiac Surgery		Development Cohort (n = 60)		Persistent AKI > 48 h	Validation Cohort (n = 148)		Persistent AKI > 48 h
AKI according to KDIGO diagnostic criteria		14	(25%)	6 (43%)	22	(15%)	9 (41%)
	KDIGO Stage 1	8	(57%)		12	(54%)
	KDIGO Stage 2	5	(36%)		8	(36%)
	KDIGO Stage 3	1	(7%)		2	(9%)
Diagnostic criteria met
	Increased creatinine	14	(100%)		22	(100%)
	Oliguria (<0.5 mL/kg/h for ≥6 h)	3	(21%)		5	(23%)
Time point of diagnosis
	24 h after surgery	3	(21%)	1 (33%)	6	(27%)	2 (33%)
	48 h after surgery	7	(50%)	3 (42%)	9	(41%)	6 (67%)
	72 h after surgery	4	(29%)	2 (50%)	7	(32%)	1 (14%)