3.1 Clinical characteristics of patients with sepssis
The process of data extraction and screening was carried out following the workflow illustrated in Figure 1. A total of 24,816 adult patients were diagnosed with sepsis and admitted to the hospital for their initial presentation. After excluding 2,658 patients with a history of prior hospitalization, 3,051 patients with malignancy, and 1,881 patients who stayed in the ICU for less than 24 hours, a total of 17,226 eligible patients were enrolled. Among them, 1,115 patients (6.47%) succumbed during their stay in the ICU. The enrolled patients had a median age of 67.65 (55.79, 78.82) years, with males accounting for 57.69% of the cohort. The baseline characteristics of the enrolled patients are presented in Table 1.
The death group exhibited significantly higher levels of age, CCI, LODS, SOFA, APS III, SAPS II scores, GCS scores, creatine levels, heart rate within 24 hours of admission to ICU compared to the survival group (P<0.001). However, the death group exhibited a lower BMI and mean body temperature during the initial 24-hour period in the ICU compared to the survivors. Additionally, the proportion of females (P=0.032) and patients receiving mechanical ventilation (P<0.001) in the death group were higher compared to those in the survival group.
Figure 1: The process of information extraction and the screening criteria for sepsis patients
Table 1: The baseline data of the enrolled patients
Variables
|
Total (n = 17226)
|
Survival (n = 16111)
|
Death (n = 1115)
|
Statistic
|
P
|
Age, Years, M (Q₁, Q₃)
|
67.65 (55.79, 78.82)
|
67.51 (55.69, 78.64)
|
70.16 (57.23, 81.64)
|
Z=-4.29
|
<0.001
|
Gender, n(%)
|
|
|
|
χ²=4.59
|
0.032
|
Female
|
7289 (42.31)
|
6783 (42.10)
|
506 (45.38)
|
|
|
Male
|
9937 (57.69)
|
9328 (57.90)
|
609 (54.62)
|
|
|
Race, n(%)
|
|
|
|
χ²=236.70
|
<0.001
|
Asian
|
438 (2.54)
|
411 (2.55)
|
27 (2.42)
|
|
|
Black
|
1306 (7.58)
|
1229 (7.63)
|
77 (6.91)
|
|
|
White
|
11450 (66.47)
|
10867 (67.45)
|
583 (52.29)
|
|
|
Hispanic / Latino
|
550 (3.19)
|
518 (3.22)
|
32 (2.87)
|
|
|
Other
|
744 (4.32)
|
706 (4.38)
|
38 (3.41)
|
|
|
Unknown
|
2738 (15.89)
|
2380 (14.77)
|
358 (32.11)
|
|
|
BMI, kg/m2, M (Q₁, Q₃)
|
28.30 (24.60, 33.10)
|
28.40 (24.60, 33.10)
|
27.90 (24.13, 32.90)
|
Z=2.02
|
0.043
|
SOFA, score, M (Q₁, Q₃)
|
3.00 (2.00, 4.00)
|
3.00 (2.00, 4.00)
|
4.00 (2.00, 6.00)
|
Z=-12.29
|
<0.001
|
CCI, score, M (Q₁, Q₃)
|
4.00 (3.00, 6.00)
|
4.00 (3.00, 6.00)
|
5.00 (3.00, 7.00)
|
Z=-9.43
|
<0.001
|
Creatinine, mg/dL, M(Q₁, Q₃)
|
1.00 (0.70, 1.50)
|
1.00 (0.70, 1.50)
|
1.30 (0.90, 2.10)
|
Z=-13.90
|
<0.001
|
GCS, score, M (Q₁, Q₃)
|
15.00 (15.00, 15.00)
|
15.00 (15.00, 15.00)
|
15.00 (15.00, 15.00)
|
Z=-0.81
|
0.415
|
APS III, score, M (Q₁, Q₃)
|
45.00 (33.00, 60.00)
|
44.00 (32.00, 59.00)
|
66.00 (50.00, 88.00)
|
Z=-28.63
|
<0.001
|
LODS, score, M (Q₁, Q₃)
|
5.00 (3.00, 7.00)
|
5.00 (3.00, 7.00)
|
8.00 (6.00, 10.00)
|
Z=-29.01
|
<0.001
|
SAPS II, score, M (Q₁, Q₃)
|
37.00 (30.00, 47.00)
|
37.00 (29.00, 46.00)
|
49.00 (39.00, 61.00)
|
Z=-26.20
|
<0.001
|
Heart Rate, bpm, M (Q₁, Q₃)
|
84.62 (75.39, 96.26)
|
84.42 (75.33, 95.92)
|
87.68 (76.44, 102.18)
|
Z=-5.71
|
<0.001
|
SBP, mmHg, M (Q₁, Q₃)
|
113.54 (105.64, 124.04)
|
113.79 (105.90, 124.17)
|
110.08 (102.32, 122.32)
|
Z=-7.72
|
<0.001
|
DBP, mmHg, M (Q₁, Q₃)
|
60.20 (54.45, 66.95)
|
60.23 (54.52, 66.85)
|
59.56 (53.03, 68.30)
|
Z=1.12
|
0.262
|
Respiratory rate, insp/min, M (Q₁, Q₃)
|
18.80 (16.65, 21.73)
|
18.68 (16.58, 21.54)
|
20.78 (18.21, 24.32)
|
Z=-16.17
|
<0.001
|
Temperature, ℃, M (Q₁, Q₃)
|
36.87 (36.59, 37.23)
|
36.87 (36.60, 37.23)
|
36.76 (36.32, 37.20)
|
Z=8.40
|
<0.001
|
Diabetes with complication, n(%)
|
|
|
|
χ²=0.18
|
0.675
|
NO
|
15636 (90.77)
|
14620 (90.75)
|
1016 (91.12)
|
|
|
YES
|
1590 (9.23)
|
1491 (9.25)
|
99 (8.88)
|
|
|
Mechanical ventilation, n(%)
|
|
|
|
χ²=47.05
|
<0.001
|
NO
|
5748 (37.51)
|
5454 (38.25)
|
294 (27.68)
|
|
|
YES
|
9574 (62.49)
|
8806 (61.75)
|
768 (72.32)
|
|
|
M: Median; Q₁: 1st Quartile; Q₃: 3st Quartile
Z: Mann,Whitney test; χ²: Chi,square test
Abbreviation: BMI: Body Mass Index; SOFA: Sequential Organ Failure Assessment; CCI: Charlson comorbidity index; GCS: Glasgow Coma Scale; APS III: Acute Physiology Score III; LODS: Logistic Organ Dysfunction Score; SAPS II: Simplified acute physiology score II; SBP: systolic blood pressure; DBP: diastolic blood pressure;
3.2 The effectiveness of five scoring systems in predicting ICU mortality
The ROC curve demonstrated that both APS III (AUC: 0.756, P<0.001) and LODS (AUC: 0.758, P<0.001) score exhibited robust predictive value for ICU mortality. The AUC (0.734, P<0.001) of the SAPS II score exhibited a slightly lower value compared to that of the APS III and LODS scores (Figure.2).
Figure 2: Prediction of mortality in septic ICU patients using multiple scoring systems.
SOFA: Sequential Organ Failure Assessment; CCI: Charlson comorbidity index; APS III: Acute Physiology Score III; LODS: Logistic Organ Dysfunction Score; SAPS II: Simplified acute physiology score II; AUC:Area under the receiver operating characteristic curve; CI: confdence interval.
3.3 Regressional analysis to identify potential factors
The potential predictors identified through univariate and multivariate regression analyses, with ICU mortality as the outcome, were presented in Table 2. Multivariate regression analysis revealed that CCI (OR=1.10; 95% CI:(1.06, 1.14); P<0.001), APS III score (OR=1.01; 95% CI:(1.01, 1.02); P<0.001), LODS score (OR=1.14; 95% CI:(1.09, 1.20); P<0.001), respiratory rate (OR=1.07; 95% CI:(1.05, 1.10); P<0.001), body temperature (OR=0.75; 95% CI:(0.67, 0.85); P<0.001), and unknown race (OR=2.82; 95% CI:(2.27, 3.49); P<0.001) served as potential predictors. The integration of these indicators into a nomogram demonstrated significant clinical value (Figure.3).
Table 2: Screening of covariates as potential risk factors
Variables
|
Univariate analysis
|
Multivariate analysis
|
β
|
OR (95%CI)
|
P
|
β
|
OR (95%CI)
|
P
|
Age, Years, M (Q₁, Q₃)
|
0.01
|
1.01 (1.01, 1.01)
|
<0.001
|
|
|
|
BMI, kg/m2, M (Q₁, Q₃)
|
-0.01
|
0.99 (0.98, 1.00)
|
0.138
|
|
|
|
SOFA, score, M (Q₁, Q₃)
|
0.18
|
1.20 (1.16, 1.24)
|
<0.001
|
|
|
|
CCI, score, M (Q₁, Q₃)
|
0.11
|
1.12 (1.09, 1.15)
|
<0.001
|
0.09
|
1.10 (1.06, 1.14)
|
<0.001
|
GCS, score, M (Q₁, Q₃)
|
0.01
|
1.01 (0.97, 1.04)
|
0.739
|
|
|
|
APS III, score, M (Q₁, Q₃)
|
0.04
|
1.04 (1.03, 1.04)
|
<0.001
|
0.01
|
1.01 (1.01, 1.02)
|
<0.001
|
LODS, score, M (Q₁, Q₃)
|
0.29
|
1.33 (1.30, 1.36)
|
<0.001
|
0.13
|
1.14 (1.09, 1.20)
|
<0.001
|
SAPS II, score, M (Q₁, Q₃)
|
0.06
|
1.06 (1.05, 1.06)
|
<0.001
|
|
|
|
Heart Rate, bpm, M (Q₁, Q₃)
|
0.01
|
1.01 (1.01, 1.02)
|
<0.001
|
|
|
|
SBP, mmHg, M (Q₁, Q₃)
|
-0.01
|
0.99 (0.98, 0.99)
|
<0.001
|
0.01
|
1.01 (1.00, 1.01)
|
0.102
|
DBP, mmHg, M (Q₁, Q₃)
|
-0.00
|
1.00 (0.99, 1.00)
|
0.481
|
|
|
|
Respiratory rate, insp/min, M (Q₁, Q₃)
|
0.11
|
1.12 (1.10, 1.13)
|
<0.001
|
0.07
|
1.07 (1.05, 1.10)
|
<0.001
|
Temperature, ℃, M (Q₁, Q₃)
|
-0.55
|
0.58 (0.52, 0.64)
|
<0.001
|
-0.28
|
0.75 (0.67, 0.85)
|
<0.001
|
Creatinine, mg/dL, M(Q₁, Q₃)
|
0.10
|
1.11 (1.07, 1.14)
|
<0.001
|
|
|
|
Gender
|
|
|
|
|
|
|
Male
|
Reference
|
|
|
|
Female
|
0.14
|
1.14 (0.99, 1.33)
|
0.071
|
|
|
|
Race
|
|
|
|
|
|
|
White
|
Reference
|
Reference
|
Unknown
|
1.06
|
2.90 (2.45, 3.42)
|
<.001
|
1.04
|
2.82 (2.27, 3.49)
|
<0.001
|
Hispanic / Latino
|
0.03
|
1.03 (0.65, 1.64)
|
0.891
|
0.21
|
1.24 (0.70, 2.18)
|
0.460
|
Black
|
0.13
|
1.14 (0.85, 1.53)
|
0.395
|
0.10
|
1.11 (0.75, 1.63)
|
0.613
|
Other
|
-0.11
|
0.90 (0.59, 1.36)
|
0.615
|
-0.12
|
0.89 (0.52, 1.51)
|
0.668
|
Asian
|
0.09
|
1.09 (0.65, 1.82)
|
0.746
|
0.04
|
1.04 (0.51, 2.14)
|
0.907
|
Diabetes with complication
|
|
|
|
|
|
|
NO
|
Reference
|
|
|
|
YES
|
-0.06
|
0.94 (0.73, 1.21)
|
0.634
|
|
|
|
Mechanical ventilation
|
|
|
|
|
|
|
YES
|
Reference
|
|
|
|
NO
|
-0.49
|
0.61 (0.52, 0.72)
|
<0.001
|
|
|
|
OR: odds ratio, CI: confdence interval.
Abbreviation: BMI: Body Mass Index; SOFA: Sequential Organ Failure Assessment; CCI: Charlson comorbidity index; GCS: Glasgow Coma Scale; APS III: Acute Physiology Score III; LODS: Logistic Organ Dysfunction Score; SAPS II: Simplified acute physiology score II; SBP: systolic blood pressure; DBP: diastolic blood pressure;
Figure 3. Nomogram for the prediction of death in the ICU
CCI: Charlson comorbidity index; APS III: Acute Physiology Score III; LODS: Logistic Organ Dysfunction Score;
3.4 Predictive performance assessed in training and validation sets.
The training set comprised 12,058 patients, while the validation set included 5,168 patients. Supplementary Table 1 presents a comparison of the characteristics between these two sets. The clinical data revealed no statistically significant disparities between the randomly allocated training set and the validation set.
The ROC curve demonstrated performance in both the training and validation datasets, with respective areas under the curve of 0.803 and 0.797. The training set demonstrated predictive sensitivities and specificities of 76.1% and 70.4%, respectively. In the validation set, corresponding sensitivities were observed to be 75.5% and 71.6% (Figure.4).
Figure 4. The performance of the prediction model in both the training and validation sets. A: Evaluation of effectiveness in the training set; B: Assessment of performance in the validation set.