Table 2.

Summary of exposure by primary outcome

First author	N	# Readmitted	#Non-readmitted	Cutoff for readmission	Severity scale	Severity of illness score timinga	Score Mean (S.D.) or median (interquartile range) [absolute range]
							Readmitted	Non-Readmitted
Durbin et al.35	1803	83	82	same hospitalization	APACHE II	discharge	10.6 (5.5)	8.8 (5.2)
Chen et al.31	2250	140	2110	same hospitalization	APACHE II	admission	21.4 (8.1)b	19.8 (8.1)b
	2878	95	2782			admission	16.8 (6.8)c	13.3 (7.2)c
Cooper et al.9	121161	6371	97613	same hospitalization	APACHE III	admission	54.3 (24.3)	43.7 (22.3)
Bracco et al.36	1024	44			SAPS II	admission	22d	16d
Chung et al.32		65	65	same hospitalization	APACHE III	admission	63.3e	57.4e
Metnitz et al34	15180	780	14400	same hospitalization	SAPS II		28 (21–38)	25 (18–35)
Alban et al.29, Nishi et al.37	10840	296	10544	same hospitalization	APACHE II	admission	18.4 (8.9)	15.3 (8.5)
						discharge	15.7 (6.7)	13.8 (7.1)
					SAPS	admission	13.7 (5.8)	11.5 (5.5)
						discharge	12.2 (4.8)	10.7 (4.9)
Gajic et al.19	1131	100	1026	<7 days after ICU discharge	APACHE III	admission	58.1 (22.9)	69.6 (26.8)
						discharge	49.4 (18.2)	56.8 (18.8)
Conlon et al.38	1061	73	988	same hospitalization	APACHE II	admission	14.4 (5.1)	10.2 (6.6)
Kaben et al.39	2852	381	2471	same hospitalization	SAPS II		37.1 (16.4)	32.9 (16.3)
Campbell et al.30	4376	385	3981	same hospitalization	APACHE II	admission	20 (16–24)	17 (13–22)
					SAPS II	admission	37 (28–48)	33 (23–43)
Park et al.40	7227	873	6354	same hospitalization	APACHE II	admission	14.3 (4.5)	13.8 (4.9)
					SAPS II	admission	25.8 (10.1)	25.0 (10.6)
Chan et al.41	945	110	835	same hospitalization	APACHE II		12.80 (6.69)	11.36 (7.31)
Gerber et al.25	42	15	27	same hospitalization	APACHE II		18.7 (7.0)	21.4 (6.8)
Butler et al.42	6511	390	6121	same hospitalization	APACHE II	admission	16 (12–20)	14 (10–19)
					SAPS II	admission	31 (23–42)	29 (20–39)
Ho et al.33	16926	654	16272	same hospitalization	APACHE II		14 (13)f	14.1(13)f
Arsenault et al.43		85g		≤ 72 hours after ICU discharge	APACHE II	admission
					SAPS	discharge
Park et al. 44	4257	271	3986	same hospitalization	APACHE II	admission and discharge
Lee et al. 45	116	58	58	same hospitalization	APACHE II	admission	15 (6.8)	10.1 (5.9)
						discharge	12.1 (5.4)	7.3 (4.8)
Silva et al.46	600	44	556	same hospitalization	SAPS II	admission
						discharge
Carrillo Alcaraz et al.47	12934	730	12204	same hospitalization	SAPS II		40 (18)	30 (15)
Roehrig et al. 48	1277	126	1151	same hospitalization	APACHE II		18 (9)	13 (7)
Khaja et al.24	3724h	163	3495	same hospitalization	APACHE IV		67.5 (30.7)	88.5 (31.2)
Nassar et al.49	3993	283	3354	same hospitalization	APACHE II	admission	37 [23–51]	26 [18–36]
Renton et al.12	247103	13598	223505	same hospitalization	APACHE III		56 (42–73)	47 (34–64)
					SAPS II		31 (23–41)	26 (19–36)
Timmers et al.50	1682	141	1541	<30 days after ICU discharge	APACHE II	admission	12 (6)	11 (6)
					SAPS III	admission	46 (12)	42 (13)
Ouanes et al.20	3462	74	3360	<7days after ICU discharge	SAPS II	admission	40 (19)	33 (20)
Willsie et al.51	10324	1197	9127	<48 hrs, 48 hrs-30 days, >30 days after ICU discharge	APACHE II	admission	7.4	6.0
Lissauer et al.52	703	77	610	same hospitalization	APACHE III	admission	69.5 (54.9)	54.9 (23.5)
Yip et al.53	1599	106	1340	same hospitalization	APACHE II	discharge	20 (16–24)	19 (14–24)

^aAdmission = index admission unless otherwise specified;

^bAcademic hospital;

^cCommunity hospital;

^dp=0.001;

^ep=0.05;

^fReported as median and SD;

^gTotal N – number in each group not reported;

^hUnit of analysis is number of readmissions