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 |
|---|---|---|---|---|
| Selection323 | Were the comparison groups appropriate?712 | - | ✔ | ✔ |
| Selection323 | Was administered dose or exposure level adequately randomized?710 | ✔ | - | ✔ |
| Selection323 | Was allocation to study groups adequately concealed?711 | ✔ | - | ✔ |
| Confounding324 | Does the study design or analysis account for important confounding and modifying variables?713 | - | ✔ | ✔ |
| Confounding324 | Did researchers adjust or control for other exposures that are anticipated to bias results?714 | - | - | ✔ |
| Performance325 | Did deviations from the study protocol impact the results?716 | - | - | ✔ |
| Performance325 | Were the research personnel and human subjects blinded to the study group during the study?717 | ✔ | - | ✔ |
| Performance325 | Were experimental conditions identical across study groups?715 | ✔ | - | ✔ |
| Attrition326 | Were outcome data incomplete due to attrition or exclusion from analysis?718 | ✔ | ✔ | ✔ |
| Detection327 | Can we be confident in the outcome assessment?722 | ✔ | ✔ | ✔ |
| Detection327 | Can we be confident in the exposure characterization?721 | ✔ | ✔ | ✔ |
| Detection327 | Were confounding variables assessed consistently across groups using valid and reliable measures?720 | - | - | ✔ |
| Detection327 | Were the outcome assessors blinded to study group or exposure level?719 | - | - | ✔ |
| Selective Reporting328 | Were all measured outcomes reported?723 | ✔ | ✔ | ✔ |
| Other329 | Were there any other potential threats to internal validity?724 | ✔ | ✔ | ✔ |
Selection323
Was administered dose or exposure level adequately randomized?710
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).
Was allocation to study groups adequately concealed?711
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.
Performance325
Were the research personnel and human subjects blinded to the study group during the study?717
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.
Were experimental conditions identical across study groups?715
Attrition326
Were outcome data incomplete due to attrition or exclusion from analysis?718
Attrition rates are required to be similar and uniformly low across groups with respect to withdrawal or exclusion from analysis
Detection327
Can we be confident in the outcome assessment?722
Confidence requires valid, reliable, and sensitive methods to assess the outcome and the methods should be applied consistently across groups.
Can we be confident in the exposure characterization?721
Confidence requires valid, reliable, and sensitive methods to measure exposure applied consistently across groups.
Selective Reporting328
Were all measured outcomes reported?723
Other329
Were there any other potential threats to internal validity?724
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.
Selection323
Were the comparison groups appropriate?712
Comparison group appropriateness refers to having similar baseline characteristics between the groups aside from the exposures and outcomes under study.
Confounding324
Does the study design or analysis account for important confounding and modifying variables?713
Note: a parallel question under detection bias addresses reliability of the measurement of confounding or modifying variables.
Attrition326
Were outcome data incomplete due to attrition or exclusion from analysis?718
Attrition rates are required to be similar and uniformly low across groups with respect to withdrawal or exclusion from analysis
Detection327
Can we be confident in the outcome assessment?722
Confidence requires valid, reliable, and sensitive methods to assess the outcome and the methods should be applied consistently across groups.
Can we be confident in the exposure characterization?721
Confidence requires valid, reliable, and sensitive methods to measure exposure applied consistently across groups.
Selective Reporting328
Were all measured outcomes reported?723
Other329
Were there any other potential threats to internal validity?724
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.
Selection323
Were the comparison groups appropriate?712
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?710
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).
Was allocation to study groups adequately concealed?711
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.
Confounding324
Does the study design or analysis account for important confounding and modifying variables?713
Note: a parallel question under detection bias addresses reliability of the measurement of confounding or modifying variables.
Did researchers adjust or control for other exposures that are anticipated to bias results?714
Performance325
Did deviations from the study protocol impact the results?716
Were the research personnel and human subjects blinded to the study group during the study?717
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.
Were experimental conditions identical across study groups?715
Attrition326
Were outcome data incomplete due to attrition or exclusion from analysis?718
Attrition rates are required to be similar and uniformly low across groups with respect to withdrawal or exclusion from analysis
Detection327
Can we be confident in the outcome assessment?722
Confidence requires valid, reliable, and sensitive methods to assess the outcome and the methods should be applied consistently across groups.
Can we be confident in the exposure characterization?721
Confidence requires valid, reliable, and sensitive methods to measure exposure applied consistently across groups.
Were confounding variables assessed consistently across groups using valid and reliable measures?720
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?719
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 Reporting328
Were all measured outcomes reported?723
Other329
Were there any other potential threats to internal validity?724
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.