Urinary kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin are early predictors for acute kidney injury among patients admitted to the surgical ICU

Figures & data

Figure 1. Consort flow sheet

Table 1. Patients’ distribution according to the development and severity of AKI as judged by change in serum creatinine

Time Group		T0-SCr (mg/dL)	T48-SCr (mg/dL)	∆SCr
No AKI (n = 115)		0.888 ± 0.134	1.077 ± 0.165	1.19 [IQR: 1.12–1.28]
AKI	Mild (n = 42)	0.903 ± 0.236	1.61 ± 0.42	1.8 [IQR: 1.7–1.8]
	Moderate (n = 21)	0.978 ± 0.25	2.34 ± 0.25	2.3 [IQR: 2.2–2.6]
	Severe (n = 10)	0.988 ± 0.324	3.446 ± 1.188	3.5 [IQR: 3.325–3.725]
	Total (n = 73)	0.938 ± 0.205	2.072 ± 0.778	1.9 [IQR: 1.8–2.5]
Total patients (n = 188)		0.948 ± 0.13	1.54 ± 0.72	1.19 [IQR: 1.12–1.28]

Data are presented as mean, standard deviation, median [IQR]; SCr: Serum creatinine; T0: time at admission, T48: at 48 hr after admission; ∆SCr: the extent of change in SCr; AKI: acute kidney injury.

Table 2. At admission data of patients categorized according to development and severity of AKI

Group Variable			No AKI (n = 115)	AKI (n = 73)			Statistical significance
				Mild (n = 42)	Moderate (n = 21)	Severe (n = 10)	P1	P2	P3
Age (years)			43.8 ± 10.3	41.8 ± 11	46.4 ± 10.1	47 ± 10.7	0.295	0.286	0.345
Sex		Males	78 (67.8%)	24 (57.1%)	13 (61.9%)	6 (60%)	0.214	0.596	0.613
		Females	37 (32.2%)	18 (42.9%)	8 (38.1%)	4 (40%)
Weight (kg)			84.6 ± 6.5	84.8 ± 6.9	84 ± 6.9	85.8 ± 6.6	0.885	0.681	0.586
Height (cm)			170.3 ± 3.2	169.9 ± 2.7	169.3 ± 2.6	171 ± 3.4	0.426	0.153	0.536
BMI (kg/m^2)			29.16 ± 2	29.37 ± 2.25	29.35 ± 6.78	29.32 ± 1.84	0.562	0.702	0.807
APACHE II score			16 ± 3.8	17.7 ± 3.5	18.4 ± 3.9	18.8 ± 3.7	0.101	0.109	0.093
SOFA score			9 ± 2.1	9.5 ± 1.8	9.4 ± 2.9	10.4 ± 2.2	0.214	0.286	0.371
TISS-28			32.3 ± 11.8	38.9 ± 13.4	40 ± 15	48.4 ± 1.7	0.003	0.008	0.0001
Cause of ICU admission	Cardiac		32 (27.8%)	8 (19%)	6 (28.6%)	3 (30%)	0.589	0.885	0.959
	Chest		8 (7%)	3 (7.1%)	1 (4.8%)	1 (10%)
	Abdominal		29 (25.2%)	10 (23.9%)	4 (19%)	2 (20%)
	Trauma		19 (16.5%)	7 (16.7%)	3 (14.3%)	1 (10%)
	Sepsis		27 (23.5%)	14 (33.3%)	7 (33.3%)	3 (10%)

Data are presented as mean, standard deviation, numbers, percentages; AKI: Acute kidney injury; BMI: Body mass index; APACHE II: Acute Physiology and Chronic Health Evaluation; SOFA: Sequential organ failure assessment; TISS-28: simplified Therapeutic Intervention Scoring System; P1 indicates the significance of difference between patients developed mild AKI and patients free of AKI; P2 indicates the significance of difference between patients developed moderate AKI and patients free of AKI; P3 indicates the significance of difference between patients developed severe AKI and patients free of AKI; P < 0.05 indicates significant difference; P > 0.05 indicates non-significant difference.

Table 3. At admission laboratory findings of studied patients categorized according to development and severity of AKI

Group Variable	No AKI	AKI			Statistical significance
		Mild	Moderate	Severe	P1	P2	P3
UCr (mg/dL)	1.29 ± 0.24	1.119 ± 0.33	1.084 ± 0.33	0.683 ± 0.28	0.00006	0.00008	<0.0001
UNGAL (ng/ml)	71.6 ± 35.7	231.1 ± 62.6	330.2 ± 107.8	429.5 ± 191.8	<0.0001	<0.0001	<0.0001
UNGAL/UCr	55.7 ± 29	221.7 ± 83.2	308.6 ± 89.6	712.5 ± 422.1	<0.0001	<0.0001	<0.0001
UKIM1 (pg/ml)	36.4 ± 18.2	119.7 ± 44.1	214.5 ± 51	232.5 ± 93.7	<0.0001	<0.0001	<0.0001
UKIM1/UCr	27.7 ± 10.3	113.5 ± 52.2	207.9 ± 66.7	370.4 ± 176.7	<0.0001	<0.0001	<0.0001

Data are presented as mean, standard deviation; AKI: Acute kidney injury; UCr: Urinary creatinine; U-NGAL: Urinary neutrophil gelatinase-associated lipocalin; U-KIM1: Urinary kidney injury molecule 1; P1 indicates the significance of difference between patients developed mild AKI and patients free of AKI; P2 indicates the significance of difference between patients developed moderate AKI and patients free of AKI; P3 indicates the significance of difference between patients developed severe AKI and patients free of AKI; P < 0.05 indicates significant difference; P > 0.05 indicates non-significant difference.

Table 4. Pearson’s correlation between development and severity of AKI as judged by ∆SCr and patients’ demographic, clinical and lab data

		∆SCr	UNGAL	UKIM1
Age	r	0.188	0.114	0.105
	P	0.010	0.672	0.781
Male gender	r	0.076	0.064	0.046
	P	0.303	0.385	0.527
BMI	r	0.157	0.104	0.095
	P	0.032	0.124	0.093
APACHE II	r	0.248	0.161	0.142
	P	0.001	0.028	0.053
SOFA	r	0.162	0.083	0.149
	P	0.026	0.259	0.042
TISS-28	r	0.331	0.316	0.269
	P	<0.001	<0.001	0.001
UNGAL	r	0.763	-	0.769
	P	<0.001	-	<0.001
UNGAL/UCr	r	0.372	-	-
	P	<0.001	-	-
UKIM1	r	0.810	0.769	-
	P	<0.001	<0.00	-
UKIM1/UCr	r	0.833	-	-
	P	<0.001	-	-

“r”: Pearson’s coefficient; ∆SCr: difference between serum creatinine at 48-hr and at admission levels; BMI: Body mass index; APACHE II: Acute Physiology and Chronic Health Evaluation; SOFA: Sequential organ failure assessment; TISS-28: simplified Therapeutic Intervention Scoring System; UCr: Urinary creatinine; U-NGAL: Urinary neutrophil gelatinase-associated lipocalin; U-KIM1: Urinary kidney injury molecule 1; P indicates the significance of the correlation; P < 0.05 indicates significant difference; P > 0.05 indicates non-significant difference.

Figure 2. ROC curve analysis for urinary markers as early predictors for upcoming AKI

Table 5. Area under the ROC curves for urinary NGAL and KIM-1 and their ratio to UCr for early prediction of AKI development within 48-hr after ICU admission

Variables	AUC	SE	95% CI	P value
UNGAL	0.589	0.042	0.508–0.678	0.039
UKIM-1	0.593	0.043	0.509–0.678	0.031
UNGAL/UCr	0.605	0.043	0.520–0.689	0.016
UKIM-1/UCr	0.686	0.038	0.610–0.761	<0.001

AUC: Area under curve; SE: Standard error; CI: Confidence interval; UCr: Urinary creatinine; U-NGAL: Urinary neutrophil gelatinase-associated lipocalin; U-KIM1: Urinary kidney injury molecule 1.