Table 1 Summary of the bias domains and prompting items for risk of bias assessment
| Â | Bias domains | ||
|---|---|---|---|
1. Study participation | 2. Study attrition | 3. Outcome measurement | |
Optimal study or characteristics of unbiased study | The study sample adequately represents the population of interest | The study data available (i.e., participants not lost to follow-up) adequately represent the study sample | The outcome of interest is measured in a similar way for all participants |
Criteria for assessment of risk of bias | Was there a representative and well-defined sample of patients? - Who did not have the outcome of interest at the time of initial observation? - Who were at a similar, identifiable, common, and possible early point in the course of the disease? | Was follow-up sufficiently complete? | Were objective and unbiased outcome criteria used? |
|  | • Definitely yes (low risk of bias) • Probably yes • Probably no • Definitely no (high risk of bias) | • Definitely yes (low risk of bias) • Probably yes • Probably no • Definitely no (high risk of bias) | • Definitely yes (low risk of bias) • Probably yes • Probably no • Definitely no (high risk of bias) |
Prompting items and considerations | a. Adequate participation in the study by eligible persons (i.e., based on inclusion/exclusion criteria) | a. Adequate response rate for study participants (less than 5% considered small loss to follow-up and more than 20% considered significant) | a. A clear definition of the outcome is provided |
| Â | b. Description of the source population or population of interest | b. Unbiased and systematic attempts to collect information on participants who dropped out | b. Method of outcome measurement used is adequately valid and reliable |
| Â | c. Description of the baseline study sample of enrolled/included patients | c. Reasons for loss to follow-up are provided | c. The method and setting of outcome measurement is the same for all study participants |
| Â | d. Adequate description of the sampling frame and recruitment | d. Adequate description of participants lost to follow-up | d. The method and setting |
| Â | e. Adequate description of the period and place of recruitment | e. There are no important differences between participants who completed the study and those who did not | Â |
| Â | f. Adequate description of inclusion and exclusion criteria | Â | Â |