Preoperative Glucose-to-Lymphocyte Ratio is an Independent Predictor for Acute Kidney Injury After Cardiac Surgery in Patients in Intensive Care Unit

Figures & data

Figure 1 Study flow diagram in the present study.

Table 1 Comparisons of Baseline Characteristics Between the Original Cohort, Matched Cohort and Weighted Cohort

Covariate	Original Cohort			Matched Cohort			Weighted Cohort
	Low GLR	High GLR	SMD	Low GLR	High GLR	SMD	Low GLR	High GLR	SMD
N	2080	5101	–	2072	2072	–	2013.77	2010.26	–
Age, years	68.1 (12.4)	69.3 (11.7)	0.095	68.1 (12.4)	67.8 (12.4)	0.020	68.3 (12.3)	68.3 (12.1)	0.002
Gender, male, n (%)	1448 (69.6)	3587 (70.3)	0.015	1444 (69.7)	1450 (70.0)	0.006	14,005.7 (69.8)	1404.2 (69.9)	0.001
BMI (kg/m^2)	28.4 (5.9)	29.1 (6.0)	0.118	28.4 (5.9)	28.5 (5.7)	0.012	28.4 (6.0)	28.4 (5.7)	0.009
Admission type, n (%)			0.250			0.095			0.007
Elective	216 (10.4)	600 (11.8)		216 (10.4)	266 (12.8)		214.4 (10.6)	224.9 (10.7)
Emergency	590 (27.9)	968 (19.0)		574 (27.7)	608 (29.3)		533.0 (26.5)	529.9 (26.4)
After surgery	568 (27.3)	1689 (33.1)		567 (27.4)	592 (28.6)		564.8 (28.0)	568.5 (28.3)
Urgent	613 (29.5)	1438 (28.2)		612 (29.5)	512 (24.7)		598.5 (29.7)	593.2 (29.5)
Observation	103 (5.0)	406 (8.0)		103 (5.0)	94 (4.5)		103.0 (5.1)	103.8 (5.2)
Surgery type, n (%)			0.073			0.017			0.009
Coronary artery	1470 (70.7)	3590 (70.4)		1465 (70.7)	1456 (70.3)		1421.5 (70.6)	1411.9 (70.2)
Valvular	538 (25.9)	1393 (27.3)		537 (25.9)	550 (26.5)		528.4 (26.2)	535.1 (26.6)
Others	72 (3.5)	118 (2.3)		70 (3.4)	66 (3.2)		63.9 (3.2)	63.3 (3.1)
Interventions, n (%)
MV use	1622 (78.0)	4409 (86.4)	0.222	1618 (78.1)	1622 (78.3)	0.005	1597.3 (79.3)	1698.9 (79.5)	0.005
CRRT use	23 (1.1)	86 (1.7)	0.049	23 (1.1)	22 (1.1)	0.005	23.0 (1.1)	22.9 (1.1)	<0.001
Vasopressors usage	1377 (66.2)	3752 (73.6)	0.161	1373 (78.1)	1386 (66.9)	0.013	1355.2 (67.3)	1353.3 (67.3)	<0.001
Score system, points
SOFA	4.8 (1.9)	5.4 (2.0)	0.206	4.8 (1.9)	4.9 (1.9)	0.021	4.8 (1.9)	4.9 (1.9)	0.013
OASIS	29.7 (7.8)	31.4 (8.0)	0.217	29.7 (7.8)	29.8 (7.9)	0.013	29.9 (7.8)	29.9 (7.9)	0.004
APSIII	38.0 (8.7)	40.6 (10.8)	0.136	38.0 (8.7)	37.7 (7.9)	0.020	38.2 (8.9)	38.4 (8.1)	0.008
SAPSII	34.6 (11.7)	37.0 (11.8)	0.204	34.6 (11.7)	34.5 (11.0)	0.009	34.8 (11.7)	34.9 (11.2)	0.009
Comorbidities, n (%)
Hypertension	1198 (57.6)	2929 (57.4)	0.004	1194 (57.6)	1206 (58.2)	0.012	1161.6 (57.7)	1250.9 (57.3)	0.009
Diabetes	686 (33.0)	1848 (36.2)	0.068	685 (33.1)	682 (32.9)	0.003	671.8 (33.4)	672.6 (33.5)	0.002
CKD	333 (16.0)	859 (16.8)	0.022	333 (16.1)	310 (15.0)	0.031	325.2 (16.1)	329.3 (16.4)	0.006
Myocardial infarct	793 (38.1)	1772 (34.7)	0.070	791 (38.2)	720 (34.7)	0.071	757.7 (37.6)	744.7 (37.0)	0.012
CHF	631 (30.3)	1594 (31.2)	0.020	629 (30.4)	610 (29.4)	0.020	613.7 (30.5)	621.4 (30.9)	0.009
Liver disease	85 (4.1)	205 (4.0)	0.003	85 (4.1)	80 (3.9)	0.012	83.1 (4.1)	84.2 (4.2)	0.003
Charlson index	5.3 (1.3)	5.4 (1.2)	0.066	5.3 (1.3)	5.2 (1.2)	0.039	5.3 (1.3)	5.3 (1.3)	0.004
Vital signs
MAP, mmHg	79.9 (15.0)	79.6 (15.5)	0.024	79.9 (15.0)	79.7 (15.1)	0.016	79.9 (14.9)	79.9 (15.7)	0.002
Heart rate, bpm	81.7 (14.0)	80.6 (13.4)	0.078	81.6 (14.0)	81.3 (14.4)	0.022	81.5 (13.9)	81.6 (14.1)	0.007
RR, bpm	16.4 (4.9)	16.6 (5.5)	0.024	16.4 (4.8)	16.7 (4.8)	0.032	16.4 (4.9)	16.4 (4.9)	0.004
SpO2, %	98.3 (3.1)	98.5 (2.8)	0.047	98.3 (3.1)	98.5 (2.4)	0.013	98.4 (3.1)	98.3 (2.9)	0.005
Laboratory results
WBC, × 10^9/L	12.0 (4.1)	12.2 (3.2)	0.036	12.0 (4.1)	12.1 (3.5)	0.013	12.0 (4.1)	12.1 (3.0)	0.011
HGB, g/dL	10.7 (2.3)	10.3 (2.2)	0.173	10.7 (2.3)	10.7 (2.3)	0.007	10.6 (2.3)	10.7 (2.3)	0.006
PLT, × 10^9/L	192.2 (58.1)	172.8 (48.5)	0.232	191.6 (57.4)	193.3 (58.8)	0.018	189.2 (57.1)	189.8 (58.7)	0.007
Albumin, mg/dL	3.6 (0.6)	3.5 (0.6)	0.147	3.6 (0.6)	3.6 (0.6)	0.010	3.6 (0.6)	3.6 (0.6)	0.009
Anion gap, mEq/L	13.3 (3.8)	13.0 (3.9)	0.080	13.3 (3.8)	13.3 (3.9)	0.009	13.2 (3.8)	13.3 (3.9)	0.013
Bicarbonate, mEq/L	23.6 (3.4)	23.1 (3.2)	0.165	23.6 (3.4)	23.6 (3.5)	0.006	23.6 (3.8)	23.5 (3.5)	0.007
BUN, mg/dL	22.5 (5.1)	20.6 (3.9)	0.127	22.4 (5.7)	22.8 (4.6)	0.027	22.0 (5.1)	22.2 (6.3)	0.014
Creatinine, mg/dL	1.2 (0.4)	1.2 (0.5)	0.021	1.2 (0.4)	1.1 (0.3)	0.026	1.2 (0.4)	1.2 (0.5)	0.012
Potassium, mmol/L	4.2 (0.6)	4.3 (0.6)	0.168	4.2 (0.6)	4.3 (0.6)	0.022	4.2 (0.6)	4.3 (0.6)	0.022
Sodium, mmol/L	138.7 (3.7)	138.4 (3.5)	0.078	138.7 (3.7)	138.5 (3.6)	0.042	138.7 (3.7)	138.6 (3.5)	0.003
AKI stages, n (%)			0.569			0.427			0.440
No AKI	957 (46.0)	1057 (20.7)		950 (45.8)	536 (25.9)		912.1 (45.3)	503.5 (25.0)
Stage I	438 (21.1)	1318 (25.8)		437 (21.1)	590 (28.5)		425.6 (21.1)	528.5 (26.3)
Stage II	576 (27.7)	2319 (45.5)		576 (27.8)	806 (38.9)		567.8 (28.2)	842.8 (41.9)
Stage III	109 (5.2)	407 (8.0)		109 (5.3)	140 (6.8)		108.4 (5.4)	135.5 (6.7)

Note: For all continuous covariates, the mean values and standard deviations are reported.

Abbreviations: GLR, glucose-to-lymphocyte ratio; SMD, standardized mean difference; MV, mechanical ventilation; RRT, renal replacement therapy; SOFA, sequential organ failure assessment; OASIS, oxford acute severity of illness score; APSIII, acute physiology score III; SAPS II, Simplified Acute Physiology Score II; CKD, chronic kidney disease; CAD, coronary artery disease; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; MAP, mean arterial pressure; RR, respiratory rate; WBC, white blood cell; HGB, hemoglobin; PLT, platelet; BUN, blood urea nitrogen.

Figure 2 Standardized mean difference (SMD) of variables before and after propensity score matching and weighting.

Table 2 Summary of Results of Primary Outcome

	Original Cohort		Matched Cohort		Weighted Cohort
	OR (95% CI)	P value	OR (95% CI)	P value	OR (95% CI)	P value
Unadjusted	3.26 (2.92–3.64)	<0.001	2.43 (2.13–2.77)	<0.001	2.48 (2.21–2.78)	<0.001
Model 1	3.10 (2.71–3.49)	<0.001	2.63 (2.29–3.02)	<0.001	2.65 (2.35–2.98)	<0.001
Model 2	3.14 (2.80–3.53)	<0.001	2.64 (2.30–3.04)	<0.001	2.66 (2.36–3.00)	<0.001
Model 3	3.01 (2.66–3.41)	<0.001	3.03 (2.61–3.53)	<0.001	3.02 (2.65–3.43)	<0.001
Model 4	3.24 (2.85–3.70)	<0.001	3.28 (2.81–3.84)	<0.001	3.16 (2.77–3.61)	<0.001

Notes: Model 1 adjusted for age, gender, BMI, admission type, surgery type. Model 2 adjusted for model 1 plus comorbidities. Model 3 adjusted for Model 2 plus score system, interventions. Model 4 adjusted for model 3 plus vital signs and laboratory results.

Table 3 NRI and IDI Analyses for Risk Reclassification of AKI in Original Cohort and Matched Cohort

Outcome	AUC				IDI		NRI^a
	Biomarker	Biomarker+ Clinical Model	Clinical Model^b	P value^c	Value (95% CI)	P value	Value (95% CI)	P value
Original cohort
GLR	0.716	0.832	0.792	<0.001	0.082 (0.076–0.089)	<0.001	0.162 (0.141–0.184)	<0.001
SOFA	0.671	0.790		0.274	0.003 (0.002–0.005)	<0.001	0.001 (−0.008–0.011)	0.785
GLR+SOFA	0.757	0.833		<0.001	0.085 (0.078–0.092)	<0.001	0.166 (0.144–0.188)	<0.001
Matched cohort
GLR	0.755	0.835	0.781	<0.001	0.105 (0.096–0.114)	<0.001	0.231 (0.202–0.261)	<0.001
SOFA	0.666	0.780		0.593	0.003 (0.001–0.005)	0.005	0.014 (0.004–0.258)	0.007
GLR+SOFA	0.759	0.836		<0.001	0.107 (0.098–0.117)	<0.001	0.245 (0.215–0.275)	<0.001

Notes: ^aThe NRI is calculated through two-way category by using the event rate of AKI. ^bThe clinical model for predicting AKI are composed of age, gender, BMI, admission type, surgery type, comorbidities, Charlson index, interventions, score system (excluding SOFA score), vital signs and laboratory results. ^cBiomarker+clinical model versus clinical model.

Abbreviations: AUC, area under the receiver-operating characteristic curve; AKI, acute kidney injury; IDI, integrated discrimination improvement; NRI, Net reclassification index; GLR, glucose to lymphocyte ratio, SOFA, sequential organ failure assessment.

Figure 3 Decision curve analysis for preoperative GLR and clinical model to detect its clinical usefulness in the original cohort (A) and in the matched cohort (B).