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Table 1 Characteristics of included studies

From: Anion gap as a prognostic tool for risk stratification in critically ill patients – a systematic review and meta-analysis

First author/year

Nr

Country

Setting and most frequent reasons for admission

Study design

Age (mean or mdn)

Sample size

Male (%)

Outcome (mortality)

Total mortality (%)

Severity of illness (mean score ± SD or mdn and range or IQR)

Antonini 2008 [17]

1

Italy

General ICU admissions: 36 % trauma; 26 % cerebrovascular disease; 14 % sepsis

Pro

Mean: 53

136

71

28-day

27

SOFA: 6 (range 0–18)

SAPS II: 40 (range 6–76)

Attanà 2013 [18]

2

Italy

STEMI patients with persistent cardiogenic shock after primary PCI admitted to ICCU

Pro

Mean: 73

63

62

In-ICCU

49

APACHE II: 20.6 ± 12.4

Boniatti 2011 [27]

3

Brazil

General ICU admissions: 64 % medical admissions; 27 % sepsis; 24 % elective surgery; 12 % emergency surgery

Pro

Mean: 56

175

53

In-hospital

37

APACHE II: 20.8 ± 8.0

SOFA score: 6.2 ± 3.8

Cusack 2002 [19]

4

UK

General ICU admissions: 17 % respiratory failure; 11 % post-cardiac arrest; 8 % trauma

Pro

Mean: 61

100

NA

28-day

31

APACHE II: 20.5

Dondorp 2004 [29]

5

Vietnam

Patients with severe falciparum malaria admitted to ICU

Pro

Mdn: 31

268

80

Not defined

17

GCS < 11: 51 %

8 % Haemodynamic shocka

Dubin 2007 [37]

6

Argentina

General ICU admissions: 56 % medical admissions; 35 % elective surgery; 9 % emergency surgery

Pro

Mean: 65

935

49

30-day

11

APACHE II: 13 ± 7

SOFA: 3 ± 3

FitzSullivan 2005 [20]

7

USA

Trauma ICU admissions: 60 % blunt trauma

Retro

Mean: 36

3102

81

In-hospital

17

APACHE II: 26.1 ± 10.5

ISS: 20.4 ± 12.9

Hucker 2005 [21]

8

UK

A&E admissions: 46 % medical admissions; 17 % elderly care; 16 % discharged

Pro

Mean: 67

672

NA

In-hospital

12

93 % alert on AVPU scale

Kaplan 2004 [7]

9

USA

Trauma patients requiring vascular repair of torso or extremities, trauma centre: 83 % penetrating trauma

Retro

Mean: 32

282

NA

28-day

23

ISS: 15.8 ± 11.0

Kaplan 2008 [16]

10

USA

Major trauma patients, trauma centre: 59 % blunt trauma

Retro

Mean: 33

78

44

28-day in hospital

33

ISS: 8.9 ± 7.3

Lazzeri 2010 [22]

11

Italy

STEMI patients admitted to ICCU at tertiary centre undergoing primary PCI

Pro

Mdn: 67

445

75

In-hospital

10

92 % Killip class I-II

8 % Killip class II-IV

41 % complications in ICCU

Lipnick 2013 [13]

12

USA

General ICU admissions: 57 % medical; 44 % surgical; 16 % sepsis

Retro

Mean: 65

664

55

30-day

15

33 % no organ failure

53 % 1–2 organs failed

14 %% ≥ 3 organs failedb

Martin 2013 [23]

13

Germany

Surgical ICU admissions: 17 % maxillofacial surgery; 13 % ENT; 12 % neurosurgery

Retro

Mean: 59

1551

54

In-hospital

9

Average length of stay in ICU: 4.2 days

Martin 2005a [25]

14

USA

Surgical ICU admissions: 56 % abdominal; 18 % vascular; 10 % thoracic

Retro

Mean: 52

2291

61

In-ICU

8

APACHE II: 21.8 ± 9.7

SAPS: 16.8 ± 8.8

Martin 2005b [24]

15

USA

Trauma patients, trauma centre: 65 % blunt trauma

Retro

Mean: 38

427

79

In-hospital

10

ISS: 23 ± 23

Novovic 2014 [28]

16

Serbia

ICU patients requiring mechanical ventilation

Retro

Mean: 60

142

47

28-day

52

APACHE II: 16.2 ± 6.4

Rocktaeschel 2003 [8]

17

Australia

General ICU admissions: 91 % respiratory; 54 % gastrointestinal; 51 % cardiovascular

Retro

Mdn: 65

300

58

In-hospital

28

APACHE II: 17 (IQR 14 – 22)

Sahu 2006 [26]

18

USA

Patients with acute MI admitted to coronary care unit: 65 % STEMI

Retro

Mean: 63

773

62

In-hospital

11

5 % cardiogenic shock

Shane 2014 [30]

19

Uganda

Major trauma patients, trauma centre: 65 % road traffic accidents; 35 % assault

Pro

Mean: 26

93

81

In-hospital

34

ISS: 25.4 ± 8.3

  1. APACHE II Acute Physiology and Chronic Health Evaluation, AVPU alert, verbal, pain, unresponsive, ENT ear, nose and throat, GCS Glasgow coma scale, ICCU intensive cardiac care unit, ICU intensive care unit, IQR interquartile range, ISS Injury Severity Score, Mdn median, MI myocardial infarction, PCI percutaneous coronary intervention, Pro prospective, Retro retrospective, SAPS simplified acute physiology score, SD standard deviation, SOFA sequential organ failure assessment, STEMI ST-elevation myocardial infarction
  2. aBased on data of previously published original study including 346 patients [38]
  3. bBased on data from entire study cohort of 18,995 patients