Risk of bias requirements
When a study is entered into the HAWC database for use in an assessment, risk of bias metrics can be entered for a metric of bias for each study. Risk of Bias metrics are organized by domain. The following questions are required for evaluation for this assessment.
Requirements by Study Type
| Domain | Metric | Bioassay | Epidemiology | In Vitro |
|---|---|---|---|---|
| Confounding2 | Did researchers adjust or control for other exposures that are anticipated to bias results?19 | ✔ | ✔ | ✔ |
| Confounding2 | Does the study design or analysis account for important confounding and modifying variables?20 | ✔ | ✔ | ✔ |
| Performance3 | Did deviations from the study protocol impact the results?21 | ✔ | ✔ | ✔ |
| Performance3 | Were experimental conditions identical across study groups?22 | ✔ | ✔ | ✔ |
| Performance3 | Were the research personnel and human subjects blinded to the study group during the study?23 | ✔ | ✔ | ✔ |
| Attrition4 | Were outcome data incomplete due to attrition or exclusion from analysis?24 | ✔ | ✔ | ✔ |
| Detection5 | Can we be confident in the exposure characterization?25 | ✔ | ✔ | ✔ |
| Detection5 | Can we be confident in the outcome assessment?26 | ✔ | ✔ | ✔ |
| Detection5 | Were confounding variables assessed consistently across groups using valid and reliable measures?27 | ✔ | ✔ | ✔ |
| Detection5 | Were the outcome assessors blinded to study group or exposure level?28 | ✔ | ✔ | ✔ |
| Selective Reporting6 | Were all measured outcomes reported?29 | ✔ | ✔ | ✔ |
| Other7 | Were there any other potential threats to internal validity?30 | ✔ | ✔ | ✔ |
| Selection1 | Was allocation to study groups adequately concealed?17 | ✔ | ✔ | ✔ |
| Selection1 | Were the comparison groups appropriate?18 | ✔ | ✔ | ✔ |
| Selection1 | Was administered dose or exposure level adequately randomized?16 | ✔ | ✔ | ✔ |
Confounding2
Did researchers adjust or control for other exposures that are anticipated to bias results?19
Does the study design or analysis account for important confounding and modifying variables?20
Note: a parallel question under detection bias addresses reliability of the measurement of confounding or modifying variables.
Performance3
Did deviations from the study protocol impact the results?21
Were experimental conditions identical across study groups?22
Were the research personnel and human subjects blinded to the study group during the study?23
Blinding requires that study scientists do not know which administered dose or exposure level the human subject or animal is being given (i.e., study group). Human studies also require blinding of the human subjects when possible.
Attrition4
Were outcome data incomplete due to attrition or exclusion from analysis?24
Attrition rates are required to be similar and uniformly low across groups with respect to withdrawal or exclusion from analysis
Detection5
Can we be confident in the exposure characterization?25
Confidence requires valid, reliable, and sensitive methods to measure exposure applied consistently across groups.
Can we be confident in the outcome assessment?26
Confidence requires valid, reliable, and sensitive methods to assess the outcome and the methods should be applied consistently across groups.
Were confounding variables assessed consistently across groups using valid and reliable measures?27
Consistent application of valid, reliable, and sensitive methods of assessing important confounding or modifying variables is required across study groups.
Note, a parallel question under selection bias addresses whether design or analysis account for confounding.
Were the outcome assessors blinded to study group or exposure level?28
Blinding requires that outcome assessors do not know the study group or exposure level of the human subject or animal when the outcome was assessed.
Selective Reporting6
Were all measured outcomes reported?29
Other7
Were there any other potential threats to internal validity?30
On a project specific basis, additional questions for other potential threats to internal validity can be added and applied to study designs as appropriate.
Examples may include inappropriate statistical methods, etc.
Selection1
Selection domain description.
Was allocation to study groups adequately concealed?17
Allocation concealment requires that research personnel do not know which administered dose or exposure level is assigned at the start of a study. Human studies also require that allocation be concealed from human subjects prior to entering the study.
Note:
- a question under performance bias addresses blinding of personnel and human subjects to treatment during the study;
- a question under detection bias addresses blinding of outcome assessors.
Were the comparison groups appropriate?18
Comparison group appropriateness refers to having similar baseline characteristics between the groups aside from the exposures and outcomes under study.
Was administered dose or exposure level adequately randomized?16
Randomization requires that each human subject or animal had an equal chance of being assigned to any study group including controls (e.g., use of random number table or computer generated randomization).
Confounding2
Did researchers adjust or control for other exposures that are anticipated to bias results?19
Does the study design or analysis account for important confounding and modifying variables?20
Note: a parallel question under detection bias addresses reliability of the measurement of confounding or modifying variables.
Performance3
Did deviations from the study protocol impact the results?21
Were experimental conditions identical across study groups?22
Were the research personnel and human subjects blinded to the study group during the study?23
Blinding requires that study scientists do not know which administered dose or exposure level the human subject or animal is being given (i.e., study group). Human studies also require blinding of the human subjects when possible.
Attrition4
Were outcome data incomplete due to attrition or exclusion from analysis?24
Attrition rates are required to be similar and uniformly low across groups with respect to withdrawal or exclusion from analysis
Detection5
Can we be confident in the exposure characterization?25
Confidence requires valid, reliable, and sensitive methods to measure exposure applied consistently across groups.
Can we be confident in the outcome assessment?26
Confidence requires valid, reliable, and sensitive methods to assess the outcome and the methods should be applied consistently across groups.
Were confounding variables assessed consistently across groups using valid and reliable measures?27
Consistent application of valid, reliable, and sensitive methods of assessing important confounding or modifying variables is required across study groups.
Note, a parallel question under selection bias addresses whether design or analysis account for confounding.
Were the outcome assessors blinded to study group or exposure level?28
Blinding requires that outcome assessors do not know the study group or exposure level of the human subject or animal when the outcome was assessed.
Selective Reporting6
Were all measured outcomes reported?29
Other7
Were there any other potential threats to internal validity?30
On a project specific basis, additional questions for other potential threats to internal validity can be added and applied to study designs as appropriate.
Examples may include inappropriate statistical methods, etc.
Selection1
Selection domain description.
Was allocation to study groups adequately concealed?17
Allocation concealment requires that research personnel do not know which administered dose or exposure level is assigned at the start of a study. Human studies also require that allocation be concealed from human subjects prior to entering the study.
Note:
- a question under performance bias addresses blinding of personnel and human subjects to treatment during the study;
- a question under detection bias addresses blinding of outcome assessors.
Were the comparison groups appropriate?18
Comparison group appropriateness refers to having similar baseline characteristics between the groups aside from the exposures and outcomes under study.
Was administered dose or exposure level adequately randomized?16
Randomization requires that each human subject or animal had an equal chance of being assigned to any study group including controls (e.g., use of random number table or computer generated randomization).
Confounding2
Did researchers adjust or control for other exposures that are anticipated to bias results?19
Does the study design or analysis account for important confounding and modifying variables?20
Note: a parallel question under detection bias addresses reliability of the measurement of confounding or modifying variables.
Performance3
Did deviations from the study protocol impact the results?21
Were experimental conditions identical across study groups?22
Were the research personnel and human subjects blinded to the study group during the study?23
Blinding requires that study scientists do not know which administered dose or exposure level the human subject or animal is being given (i.e., study group). Human studies also require blinding of the human subjects when possible.
Attrition4
Were outcome data incomplete due to attrition or exclusion from analysis?24
Attrition rates are required to be similar and uniformly low across groups with respect to withdrawal or exclusion from analysis
Detection5
Can we be confident in the exposure characterization?25
Confidence requires valid, reliable, and sensitive methods to measure exposure applied consistently across groups.
Can we be confident in the outcome assessment?26
Confidence requires valid, reliable, and sensitive methods to assess the outcome and the methods should be applied consistently across groups.
Were confounding variables assessed consistently across groups using valid and reliable measures?27
Consistent application of valid, reliable, and sensitive methods of assessing important confounding or modifying variables is required across study groups.
Note, a parallel question under selection bias addresses whether design or analysis account for confounding.
Were the outcome assessors blinded to study group or exposure level?28
Blinding requires that outcome assessors do not know the study group or exposure level of the human subject or animal when the outcome was assessed.
Selective Reporting6
Were all measured outcomes reported?29
Other7
Were there any other potential threats to internal validity?30
On a project specific basis, additional questions for other potential threats to internal validity can be added and applied to study designs as appropriate.
Examples may include inappropriate statistical methods, etc.
Selection1
Selection domain description.
Was allocation to study groups adequately concealed?17
Allocation concealment requires that research personnel do not know which administered dose or exposure level is assigned at the start of a study. Human studies also require that allocation be concealed from human subjects prior to entering the study.
Note:
- a question under performance bias addresses blinding of personnel and human subjects to treatment during the study;
- a question under detection bias addresses blinding of outcome assessors.
Were the comparison groups appropriate?18
Comparison group appropriateness refers to having similar baseline characteristics between the groups aside from the exposures and outcomes under study.
Was administered dose or exposure level adequately randomized?16
Randomization requires that each human subject or animal had an equal chance of being assigned to any study group including controls (e.g., use of random number table or computer generated randomization).