SAPS 3 is not superior to SAPS 2 in cardiac surgery patients

Figures & data

Table I. SAPS 2.

Table II. SAPS 3.

Table III. Patients’ data and operations during the study period.

Age	67.2 ± 10.9 years
Length of ICU stay	4.6 ± 7.0 days
Additive EuroSCORE	6.3 ± 3.7
Logistic EuroSCORE	9.9 ± 12.9
Category	Number	%
Male	3249	62.4
Female	1958	37.6
ICU mortality	305	5.9
CABG	2755	52.9
Isolated valve surgery	1187	22.8
Combined CABG and valve surgery	692	13.3
Aortic surgery	323	6.2
Cardiac transplantation	52	1.0
Others (including congenital heart defect, tumors, pulmonary embolectomy, assist device implantation)	198	3.8
Total operations	5207

Proportion of length of ICU stay and the respective mortality
Days on ICU	Total number of patients	Survivors in %	Non-survivors in %
1 or 2	2824	97.8	2.2
3–5	1482	93.5	6.5
6–8	388	90.7	9.3
9–12	156	80.8	19.2
≥ 13	357	77.3	22.7

CABG, coronary artery bypass grafting; ICU, intensive care unit.

Table IV. Statistical results.

Day (Number of patients at risk)	Scoring model	OCC^e %	ROC-analysis^g		DeLong p value^f	Calibr. HL test^c
			AUC^b	95%-CI^a		Chi²	p value
ICU-day^d 1 (5207)	SAPS^h 2	94.4	0.804	0.780–0.828	0.010	39.968	0.000
	SAPS 3	94.4	0.757	0.725–0.789		46.746	0.000
ICU-day 2 (5159)	SAPS 2	94.3	0.875	0.851–0.890	0.358	57.752	0.000
	SAPS 3	95.2	0.893	0.861–0.925		15.175	0.056
ICU-day 3 (2372)	SAPS 2	89.4	0.873	0.858–0.888	0.310	27.799	0.001
	SAPS 3	91.0	0.861	0.844–0.879		16.411	0.037
ICU-day 4 (1612)	SAPS 2	87.7	0.849	0.837–0.860	0.026	23.296	0.003
	SAPS 3	87.8	0.828	0.814–0.842		10.175	0.253
ICU-day 5 (1164)	SAPS 2	86.0	0.838	0.828–0.849	0.002	20.356	0.009
	SAPS 3	85.9	0.815	0.804–0.826		13.142	0.107
ICU-day 6 (889)	SAPS 2	84.2	0.809	0.800–0.818	0.008	16.759	0.033
	SAPS 3	84.5	0.825	0.817–0.834		2.860	0.943
ICU-day 7 (713)	SAPS 2	83.0	0.787	0.778–0.796	0.007	12.528	0.129
	SAPS 3	83.0	0.803	0.796–0.811		2.043	0.980
ICU-day 8 (601)	SAPS 2	78.9	0.777	0.769–0.784	0.140	23.055	0.003
	SAPS 3	82.7	0.784	0.777–0.792		4.366	0.823

Results of overall correct classification, discrimination (receiver operating characteristic), AUC comparison by DeLong's method, and calibration (HL test) for the two SAPS models from Day 1 until Day 8.

^a95%-CI: 95%-confidence interval.

^bAUC: area under ROC-curve.

^cCalibr. HL test: calibration Hosmer–Lemeshow test.

^dICU-day: intensive care unit day

^eOCC: overall correct classification

^fp value of DeLong's method, which compares the SAPS 2 and SAPS 3 models.

^gROC: receiver operating characteristic.

^hSAPS: Simplified Acute Physiology Score.

Figure 1. SAPS 2 and SAPS 3 on ICU Days 1 and 2.