Table 2 Risk of bias scoring
Participant selection | Score |
|---|---|
Cohort studies | |
 Selected cohort is very representative of the general hospitalised population | 2 |
 Selected cohort is somewhat representative of the general hospitalised population | 1 |
 Cohort is not representative of the general hospital population or the selection of the group was not described | 0 |
Case-control studies | |
 Cases and controls drawn from the same population and population is very representative of the general hospitalised population | 2 |
 Cases and controls drawn from the same population and population is somewhat representative of the general hospitalised population | 1 |
 Cases and controls drawn from different sources or the selection of groups was not described | 0 |
Comparability of groups | |
 No differences between the groups explicitly reported unless it was one of these variables that was under investigation, or such differences were adjusted for | 2 |
 Differences between groups were not recorded | 1 |
 Groups differed | 0 |
Size | |
 >100 participants in each group | 2 |
 <100 participants in each group | 1 |
 Adjustment for confounding | 1 |
 Adjustment made for confounding factors in data analysis | 1 |
 No adjustment for cofounders | 0 |