A nomogram based on serum cystatin C for predicting acute kidney injury in patients with traumatic brain injury

Figures & data

Table 1. Baseline characteristics of non-AKI group and AKI group in included TBI patients.

Variables	Overall patients (N = 234)	Non-AKI group (n = 179)	AKI group (n = 55)	p Value
Age (years)	44 (28–59)	43 (27–56)	47 (34–64)	0.092
Sex (male ratio)	182 (77.8%)	136 (76%)	46 (83.6%)	0.220
Injury mechanism
Traffic accident	148 (63.2%)	112 (62.6%)	36 (65.5%)	0.697
High falling	49 (20.9%)	37 (20.7%)	12 (21.8%)	0.855
Stumble	22 (9.4%)	15 (8.4%)	7 (12.7%)	0.349
Others	15 (6.4%)	15 (8.4%)	0	0.025
Vital signs on admission
Systolic blood pressure (mmHg)	123 (108–141)	125 (110–141)	120 (103–146)	0.326
Diastolic blood pressure (mmHg)	73.79 ± 16.58	74.07 ± 15.32	72.87 ± 20.29	0.687
Heart rate (min^−1)	98 (81–120)	96 (80–116)	107 (86–121)	0.066
Body temperature (°C)	36.8 (36.5–37.1)	36.8 (36.5–37.1)	36.8 (36.5–37.8)	0.610
Respiratory rate (min^−1)	20 (17–23)	20 (17–23)	20 (16–22)	0.615
Anisocoria	84 (35.9%)	64 (35.8%)	20 (36.4%)	0.934
GCS	6 (4–8)	6 (5–9)	5 (3–6)	<0.001
Laboratory tests
White blood cell (10^9/L)	15.09 (11.14–20.43)	14.84 (11.27–19.49)	15.76 (10.58–23)	0.362
Neutrophil (10^9/L)	11.61 (8.64–15.77)	11.38 (8.77–15.60)	12.32 (7.67–17.54)	0.927
Lymphocyte (10^9/L)	0.82 (0.54–1.16)	0.84 (0.55–1.22)	0.75 (0.46–1.02)	0.071
Platelet (10^9/L)	115 (78–169)	125 (86–179)	89 (54–136)	<0.001
Hemoglobin (g/L)	88 (77–106)	92 (79–110)	80 (72–91)	0.001
Fibrinogen (mg/L)	2.88 (1.68–4.27)	3.07 (1.78–4.45)	2.22 (1.23–4.06)	0.044
Albumin (g/L)	31.2 ± 5.9	31.8 ± 6.0	29.2 ± 5.4	0.004
Cholesterol (mmol/L)	2.66 (1.95–3.51)	2.82 (2.21–3.67)	2.02 (1.44–2.76)	<0.001
Lactate dehydrogenase (U/L)	380 (291–533)	363 (270–491)	474 (344–726)	<0.001
Blood urea nitrogen (mmol/L)	6.11 (4.70–8.67)	5.77 (4.43–7.77)	9.34 (5.8–14.61)	<0.001
Serum creatinine (umol/L)	71 (56–98)	65 (51–81)	124 (98–172)	<0.001
Serum cystatin C (mg/L)	0.78 (0.63–0.97)	0.72 (0.60–0.89)	1.09 (0.85–1.65)	<0.001
Radiological findings
Epidural hematoma	30 (12.8%)	29 (16.2%)	1 (1.8%)	0.001
Subdural hematoma	93 (39.7%)	71 (39.7%)	22 (40%)	0.965
Intracerebral hematoma	81 (34.6%)	61 (34.1%)	20 (36.4%)	0.756
Subarachnoid hemorrhage	102 (43.6%)	80 (44.7%)	22 (40%)	0.538
Intraventricular hemorrhage	15 (6.4%)	12 (6.7%)	3 (5.5%)	1.000
Diffused axonal injury	35 (15%)	29 (16.2%)	6 (10.9%)	0.321
Treatment options
Transfusion of RBC	86 (36.8%)	57 (31.8%)	29 (52.7%)	0.006
Mannitol	174 (74.4%)	136 (76.0%)	38 (69.1%)	0.313
Fructose glycerol	25 (10.7%)	20 (11.2%)	5 (9.1%)	0.657
Hypertonic saline	84 (35.9%)	74 (41.3%)	10 (18.2%)	0.001
Decompressive craniectomy	86 (36.8%)	63 (35.2%)	23 (41.8%)	0.376
Hematoma evacuation	98 (41.9%)	75 (41.9%)	23 (41.8%)	0.991
Length of ICU stay (days)	13 (2–25)	14 (4–25)	5 (2–27)	0.057
Length of hospital stay (days)	22 (8–39)	24 (11–41)	9 (3–29)	<0.001
In-hospital mortality	95 (40.6%)	54 (30.2%)	41 (74.5%)	<0.001

GCS: Glasgow Coma Scale; RBC: red blood cell.

Table 2. Univariate and multivariate logistic regression analysis of risk factors for AKI after TBI.

	Univariate logistic regression analysis			Multivariate logistic regression analysis
Variables	OR	95% Cl	p	OR	95% Cl	p Value
Age (years)	1.015	0.999–1.032	0.065
Sex (male)	1.616	0.732–3.569	0.235
Systolic blood pressure (mmHg)	0.997	0.985–1.009	0.597
Diastolic blood pressure (mmHg)	0.996	0.978–1.014	0.638
Heart rate (min^-1)	1.009	0.998–1.021	0.104
Body temperature (°C)	1.108	0.804–1.528	0.530
Respiratory rate (min^-1)	1.004	0.950–1.061	0.894
Anisocoria	1.027	0.548–1.925	0.934
GCS	0.735	0.633–0.854	<0.001
White blood cell (10^9/L)	1.030	0.987–1.075	0.177
Neutrophil (10^9/L)	0.997	0.977–1.019	0.815
Lymphocyte (10^9/L)	0.520	0.277–0.976	0.042	0.324	0.114–0.920	0.034
Platelet (10^9/L)	0.993	0.988–0.998	0.004
Hemoglobin (g/L)	0.981	0.966–0.996	0.012
Fibrinogen (mg/L)	0.877	0.743–1.035	0.120
Albumin (g/L)	0.926	0.877–0.977	0.005
Cholesterol (mmol/L)	0.479	0.336–0.684	<0.001
Lactate dehydrogenase (U/L)	1.002	1.001–1.003	0.001
Blood urea nitrogen (mmol/L)	1.334	1.199–1.485	<0.001
Serum creatinine (umol/L)	1.061	1.043–1.079	<0.001	1.052	1.031–1.074	<0.001
Serum cystatin C (mg/L)	51.742	13.176–203.187	<0.001	8.801	1.487–52.087	0.017
Epidural hematoma	0.096	0.013–0.720	0.023
Subdural hematoma	1.014	0.547–1.879	0.965
Intracerebral hematoma	1.105	0.589–2.076	0.755
Subarachnoid hemorrhage	0.825	0.446–1.525	0.540
Intraventricular hemorrhage	0.803	0.218–2.955	0.741
Diffused axonal injury	0.633	0.248–1.615	0.339
Transfusion of RBC	2.387	1.290–4.419	0.006	4.212	1.541–11.515	0.005
Mannitol	0.707	0.363–1.377	0.308
Fructose glycerol	0.795	0.284–2.227	0.663
Hypertonic saline	0.315	0.149–0.666	0.002	0.357	0.119–1.074	0.067
Decompressive craniectomy	1.323	0.714–2.454	0.374
Hematoma evacuation	0.997	0.540–1.839	0.991

OR: odds ratio; Cl: confidence interval; GCS: Glasgow Coma Scale; RBC: red blood cell.

Figure 1. ROC curves of cystatin C and constructed predictive model for predicting AKI after TBI.

Figure 2. (A) Nomogram of the constructed logistic model for predicting AKI in included TBI patients. The nomogram consisted of four variables including lymphocyte, serum creatinine, serum cystatin C and records of RBC transfusion. Based on the sum of corresponding points of each variable, total points could be calculated and therefore evaluated the risk of AKI. (B) Calibration plot for predicting AKI in included TBI patients.

Table 3. Predictive value of cystatin C and constructed model for predicting AKI after TBI.

	AUC	95% Cl	Sensitivity	Specificity
Cystatin C	0.804	0.727–0.880	0.655	0.894
Predictive model	0.925	0.883–0.967	0.764	0.961

AUC: area under the ROC curve; Cl: confidence interval.