Prediction of hospital mortality in intensive care unit patients from clinical and laboratory data: A machine learning approach

Table 1 Descriptive and univariate comparative analyses for numerical predictive variables according to outcome

Variable	mean ± SD		U value	P value
	Death outcome, n = 338	Survival outcome, n = 749
Age	63.4 ± 15.7	60.1 ± 16.1	111072	< 0.001
Disease score	1.3 ± 0.8	1.2 ± 0.7	121505.5	0.110
Eye opening (GCS)	2.0 ± 1.2	2.5 ± 1.2	97325.0	< 0.001
Heart rate	114.3 ± 34.9	111.1 ± 31.1	117672.0	0.031
Hematocrit	31.7 ± 8.3	32.8 ± 7.3	116749.0	0.02
MAP	84.7 ± 53.9	87.4 ± 48.7	108432.0	< 0.001
Max albumin	2.7 ± 0.7	2.8 ± 0.6	109136.0	< 0.001
Max bilirubin	2.2 ± 3.8	1.2 ± 1.8	98589.5	< 0.001
Max BUN	40.0 ± 25.2	33.8 ± 24.5	102300.0	< 0.001
Max calcium	8.0 ± 0.9	8.1 ± 0.8	117155.0	0.024
Max creatinine	2.6 ± 2.0	2.0 ± 1.9	96278.5	< 0.001
Max DBP	92.0 ± 23.1	94.8 ± 21.5	116162.0	0.015
Max glucose	231.4 ± 113.0	210.1 ± 105.2	11090.0	< 0.001
Max HCO3	21.0 ± 5.1	23.3 ± 4.8	94750.0	< 0.001
Max hemoglobin	11.7 ± 2.5	11.7 ± 2.3	124619.0	0.341
Max INR	2.1 ± 1.3	1.6 ± 0.8	83944.0	< 0.001
Max lactate	7.3 ± 5.5	3.2 ± 2.8	62255.5	< 0.001
Max platelets	189446.7 ± 98687.9	198186.9 ± 96842.7	120773.5	0.113
Max potassium	4.7 ± 0.9	4.5 ± 0.8	106603.0	< 0.001
Max sodium	142.1 ± 6.7	140.9 ± 5.4	113894.0	0.004
Max SBP	147.5 ± 29.3	151.1 ± 26.2	113747.5	0.004
Max SpO2	99.6 ± 1.5	99.8 ± 0.6	119714.5	0.005
Max WBC	17442.9 ± 10269.3	15302 ± 8516	111218.5	0.001
Min albumin	2.5 ± 0.7	2.7 ± 0.6	101997.5	< 0.001
Min bilirubin	1.9 ± 3.3	1.1 ± 1.7	101177.5	< 0.001
Min BUN	34.2 ± 22.9	29.0 ± 21.0	106584.5	< 0.001
Min calcium	7.4 ± 0.9	7.7 ± 0.9	98668.5	< 0.001
Min creatinine	2.08 ± 1.7	1.6 ± 1.3	99935.0	< 0.001
Min glucose	104.6 ± 47.0	110.7 ± 38.1	111941.5	0.001
Min HCO3	17.0 ± 5.5	20.6 ± 5.5	79747.5	< 0.001
Min hemoglobin	10.3 ± 2.7	10.8 ± 2.4	111370.0	0.001
Min INR	1.8 ± 0.9	1.5 ± 0.6	89909.5	< 0.001
Min lactate	4.7 ± 4.0	2.1 ± 1.58	69894.5	< 0.001
Min platelets	157252 ± 94655.6	177120.8 ± 90595.7	110075.0	< 0.001
Min potassium	3.8 ± 0.8	3.8 ± 0.7	125962.0	< 0.001
Min SBP	75.4 ± 20.3	84.9 ± 19.6	92919.0	< 0.001
Min sodium	137.9 ± 6.1	138.2 ± 5.5	121722.5	0.155
Min WBC	13247.1 ± 8505.4	12.7 ± 6.9	122208.5	0.181
Min DBP	38.7 ± 14.9	44.9 ± 12.7	93559.5	< 0.001
Min SpO2	81.3 ± 19.0	88.0 ± 12.0	94624.5	< 0.001
Motor response (GCS)	2.9 ± 2.2	4.3 ± 2.0	83488.5	< 0.001
PaCO2	40.0 ± 13.9	39.5 ± 11.6	124352.0	0.321
PaO2	137.4 ± 102.3	130.9 ± 82.4	121043.0	0.124
pH	7.3 ± 0.1	7.3 ± 0.1	109784.0	< 0.001
Respiratory rate	31.2 ± 15.1	27.5 ± 14.9	107284.5	< 0.001
Temperature	35.2 ± 1.9	36.2 ± 1.4	80674.5	< 0.001
Verbal response (GCS)	1.9 ± 1.5	2.3 ± 1.7	109666.5	< 0.001

BUN: Blood urea nitrogen; DBP: Diastolic blood pressure; GCS: Glasgow coma scale; INR: International normalized ratio; MAP: Medium Arterial Pressure; PaCO₂: Partial pressure of carbonic gas in arterial blood; PaO₂: Partial pressure of oxygen in arterial blood; SBP: Systolic blood pressure; SpO₂: Saturation of peripheral oxygen; WBC: White blood cells.

Table 2 Percentual importance of variables in the outcome prediction

Variable	Predictive importance, %
Maximum lactate	9.05
Minimum lactate	6.49
Temperature	6.47
Motor GCS	5.25
Maximum BUN	4.35
Minimum WBC	3.31
Minimum creatinine	3.22
Maximum INR	3.15
Minimum HCO3	2.84
Maximum glucose	2.69
Minimum SpO2	2.45
pH	2.18
Age	2.09
Minimum INR	1.95
Platelets	1.9
Maximum HCO3	1.83
Minimum SBP	1.82
Minimum DBP	1.82
Maximum creatinine	1.79
Minimum albumin	1.67
Minimum sodium	1.66
Predominant systemic involvement	1.64
Maximum bilirubin	1.63
Maximum WBC	1.63
PaO2	1.62
Minimum hemoglobin	1.6
Maximum SBP	1.6
Maximum albumin	1.5
MAP	1.5
Eyes opening GCS	1.46
Respiratory rate	1.41
Minimum calcium	1.4
Maximum hemoglobin	1.39
Minimum platelets	1.35
Minimum BUN	1.28
Hematocrit	1.22
Minimum bilirubin	1.2
PaCO2	1.19
Maximum sodium	1.13
Maximum DBP	1.12
Maximum calcium	0.93
Minimum glucose	0.92
Minimum potassium	0.92
Maximum potassium	0.82
Heart rate	0.72
Verbal GCS	0.42
Intubated	0.15
Disease score	0.14
Maximum SpO2	0.13

BUN: Blood urea nitrogen; DBP: Diastolic blood pressure; GCS: Glasgow coma scale; INR: International normalized ratio; MAP: Medium Arterial Pressure; PaCO₂: Partial pressure of carbonic gas in arterial blood; PaO₂: Partial pressure of oxygen in arterial blood; SBP: Systolic blood pressure; SpO₂: Saturation of peripheral oxygen; WBC: White blood cells.