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Table 1 Methodological quality (risk of bias) in cohort studies (16 items)

From: Community-onset sepsis and its public health burden: protocol of a systematic review

Definition (Item #) Study 1 {#X} Study 2 {#X} Study 3 {#X} Study 4 {#X} Study 5 {#X} Study 6 {#X} Study 7 {#X}
Internal validity
 The study addresses an appropriate and clearly focused question (Item 1)        
Selection of subjects
 The two groups being studied are selected from source populations that are comparable in all respects other than the factor under investigation (Item 2)        
 The study indicates how many of the people asked to take part did so, in each of the groups being studied (Item 3)        
 The likelihood that some eligible subjects might have the outcome at the time of enrolment is assessed and taken into account in the analysis (Item 4)        
 What percentage of individuals or clusters recruited into each arm of the study dropped out before the study was completed (Item 5)        
 Comparison is made between full participants and those lost to follow-up, by exposure status (Item 6)        
Assessment
 The outcomes are clearly defined (Item 7)        
 The assessment of outcome is made blind to exposure status. If the study is retrospective this may not be applicable (Item 8)        
 Where blinding was not possible, there is some recognition that knowledge of exposure status could have influenced the assessment of outcome (Item 9)        
 The method of assessment of exposure is reliable (Item 10)        
 Evidence from other sources is used to demonstrate that the method of outcome assessment is valid and reliable (Item 11)        
 Exposure level or prognostic factor is assessed more than once (Item 12)        
Confounding
 The main potential confounders are identified and taken into account in the design and analysis (Item 13)        
Statistical analysis        
 Have confidence intervals been provided? (Item 14)        
Overall assessment of the study
 Taking into account clinical considerations, your evaluation of the methodology used, and the statistical power of the study, do you think there is clear evidence of an association between exposure and outcome? (Item 15)        
 Are the results of this study directly applicable to the patient group targeted in this guideline? (Item 16)        
Summary quality (risk of bias) rating        
  1. Possible responses to each item: yes, no, can’t say, or doesn’t apply
  2. ≥12 items rated as ‘yes’ - high quality++ (little or no risk of bias; results unlikely to be changed by further research)
  3. 6–11 items rated as ‘yes’ - acceptable quality+ (most criteria met; some flaws in the study with an associated risk of bias; conclusions may change in the light of further studies)
  4. 0–5 items rated as ‘yes’ - low quality 0 (either most criteria not met, or significant flaws relating to key aspects of study design; conclusions likely to change in the light of further studies)