Table 1 Assessment of study quality, risk of bias, and confounding

1. Exposure definition (sepsis)

 i) Consensus [7, 8, 28–32, 35, 37, 39, 40, 44, 45, 47–50, 63–74]

49 %

 ii) Claims/ICD codes [11, 24–26, 38, 41, 58, 75–77]

14 %

 iii) Pathogen-plus (either positive blood culture or pathogen specified) [27, 34, 36, 46, 53, 78–81]

20 %

 iv) Pneumonia [33, 40, 42, 43, 52, 82–85]

15 %

 v) Peritonitis [21, 51, 86]

5 %

2. Ascertainment of exposure

 i) Claims/ICD codes data

13 %

 ii) Randomized controlled trial cohorts [44, 45, 63, 66, 69, 70]

10 %

 iii) Non-interventional study cohorts

75 %

3. Selection of the control cohort

 i) Drawn from ICU patients without sepsis

  a. Matched [35]

2 %

  b. Not matched [7, 25, 30–32, 37, 41]

12 %

 ii) Drawn from hospitalized infected patients (not ICU)

  a. Matched

  b. Not matched [30, 41]

3 %

 iii) Drawn from hospitalized non-infected patients (not ICU)

  a. Matched [36]

2 %

  b. Not matched [30, 34, 38–41]

10 %

 iv) Population controls

  a. Matched [30, 33, 37, 41–43]

10 %

  b. Not matched [40, 41]

3 %

 v) No control cohorts/no controls for mortality comparison

73 %

4. Comparability of cohorts on the basis of design or analysis

 i) Regression models to adjust for confounders

  a. Regression models in studies reporting control population

   - Post-acute mortality [7, 25, 30, 33–37, 39, 42]

16 %

   - Cumulative mortality

   - Stratified analysis for post-acute mortality [32, 40, 42, 43]

5 %

   - Non-mortality outcome models [31, 38, 41]

5 %

  b. Regression models using in studies with no controls

   - Post-acute mortality

22 %

   - Cumulative mortality

20 %

   - No mortality model

31 %

 ii) Studies reporting sepsis dose-response [39, 46, 49, 52, 53]

9 %

5. Assessment of post-acute mortality

 i) Record linkage with national or regional databases or outcome assessed by contact with patient or relatives

90 %

 ii) No description

10 %

6. Adequacy of follow up

 i) Complete follow up, all participants accounted for

22 %

 ii) Loss to follow up unlikely to introduce bias (<20 % loss, or >20 % but those lost described and unlikely to be different from those followed)

61 %

 iii) Follow up <80 % and no description of those lost

3 %

 iv) No statement

14 %

7. Report both acute and post-acute mortality (or that information can be determined from the reported data)

 i) At one year

72.9 %

 ii) Between 2 and 10 years [11, 29–32]

8.5 %

 iii) No mortality data/post-acute mortality not estimable/follow-up time unclear [21, 24–28]

10.2 %