Assessment for risk of bias
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First author | Reviewer........................ |
Biases
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Issues to consider for judging overall rating of “risk of bias”
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Study methods and comments
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Rating of risk of bias
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Assess the risk of each potential bias | These issues will guide your thinking and judgment about the overall risk of bias within each of the 6 domains. | Provide comments or excerpts to facilitate the consensus process that will follow |
High, moderate, low
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1) Study participation
| The study sample adequately represents the population of interest |
Summary
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a. Adequate participation in the study by eligible persons (> 80%) | | High bias: The relationship between the PF and outcome is very likely to be different for participants and eligible nonparticipants
Moderate bias:
The relationship between the PF and outcome may be different for participants and eligible nonparticipants Low bias: The relationship between the PF and outcome is unlikely to be different for participants and eligible nonparticipants |
b. Description of the source population or population of interest | |
c. Description of the baseline study sample | |
d. Adequate description of the sampling frame and recruitment. | |
e. Adequate description of the period and place of recruitment | |
f. Adequate description of inclusion and exclusion criteria | |
2) Study attrition
| The study data available (i.e., participants not lost to follow-up) adequately represent the study sample |
Summary
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a. Adequate response rate for study participants (> 80%) | | High bias: The relationship between the PF and outcome is very likely to be different for completing and noncompeting participants Moderate bias: The relationship between the PF and outcome may be different for completing and noncompeting participants Low bias: The relationship between the PF and outcome is unlikely to be different for completing and noncompeting participants |
b. Description of attempts to collect information on participants who dropped out | |
c. Reasons for loss to follow-up are provided | |
d. Adequate description of participants lost to follow-up | |
e. There are no important differences between participants who completed the study and who did not | |
3) Prognostic factor measurement
| The PF is measured in a similar way for all participants |
Summary
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a. A clear definition or description of the PF is provided | | High bias: The measurement of the PF is very likely to be different for different levels of the outcome of interest Moderate bias: The measurement of the PF may be different for different levels of the outcome of interest Low bias: The measurement of the PF is unlikely to be different for different levels of the outcome of interest |
b. Method of PF measurement is adequately valid and reliable (i.e., direct ascertainment; secure record, hospital record) | |
c. Continuous variables are reported or appropriate cut-points are used | |
d. The method and setting of measurement of PF is the same for all study participants | |
e. Adequate proportion of the study sample has complete data for the PF (> 80%) | |
f. Appropriate methods of imputation are used for missing PF data | |
4) Outcome measurement
| The outcome of interest is measured in a similar way for all participants |
Summary
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a. A clear definition of the outcome of interest is provided (including the time of death) | | High bias: The measurement of the outcome is very likely to be differently related to the baseline level of the PF Moderate bias: The measurement of the outcome may be differently related to the baseline level of the PF Low bias: The measurement of the outcome is unlikely to be differently related to the baseline level of the PF |
b. Method of outcome measurement used is adequately valid and reliable (i.e. independent blind assessment, hospital record or record linkage) | |
c. The method and setting of outcome measurement is the same for all study participants | |
5) Study confounding
| Important potential confounder is appropriately accounted for |
Summary
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a. Most important confounders are measured | | High bias: The observed effect of the PF on the outcome is very likely to be distorted by another factor related to PF and outcome Moderate bias: The observed effect of the PF on outcome may be distorted by another factor related to PF and outcome Low bias: The observed effect of the PF on the outcome is unlikely to be distorted by another factor related to PF and outcome |
b. Clear definitions of the important confounders measured are provided | |
c. Measurement of all important confounders is adequately valid and reliable | |
d. The method and setting of confounding measurement are the same for all study participants | |
e. Appropriate methods are used if imputation is used for missing confounder data | |
f. Important potential confounders are accounted for in the study design (by limiting the study to specific population groups, or by matching) | |
g. Important potential confounders are accounted for in the analysis (by stratification, multivariate regression) | |
6) Statistical analysis and presentation
| The statistical analysis is appropriate, and all primary outcomes are reported |
Summary
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a. Sufficient presentation of data to assess the adequacy of the analytic strategy | | High bias: The reported results are very likely to be spurious or biased related to analysis or reporting Moderate bias: The reported results may be spurious or biased related to analysis or reporting Low bias: The reported results are unlikely to be spurious or biased related to analysis or reporting |
b. Strategy for model building is appropriate and is based on a conceptual framework or model | |
c. The selected statistical model is adequate for the design of the study | |
d. There is no selective reporting of results (based on the study protocol, if available, or on the “Methods” section) | |