In Brief:
·
The risk of bias is defined as the risk
of systematic error or a deviation from reporting the truth or an appropriate
evidence finding.
·
It occurs when there is a systematic
flaw or limitations in the study design or the conduct of the study.
·
This article describes different
assessment tools and the types of study designs for which the tool is
applicable along with the flow of how to avoid the risk of bias.
A systematic reviewguideline will often determine the study
design to answer the formulated question, and it is not enough in trusting the
evidence of systematic review over observational studies. There are several
terms like quality assessment, critical appraisal, or internal validity, which
are used for the evaluation of studies supported by the guideline. Whereas in the
risk of bias, the bias determines the factor that can affect the observations and findings of the study systematically and report
it to be different from the actual conclusion. In other words, a study affected
by bias can be inaccurate and thus leads to an inappropriate guideline
recommendation. Therefore, inadequate study design or the conduct of the study
will give false findings which result in wasting time and resources, and
missing opportunity for effective intervention.
Quality assessment or risk of bias
assessment helps in regulating and establishing transparency of evidence
synthesis (data collection methods, search strategies, etc.) and findings and
it is often performed for each study in a review; thus the collected evidence eliminate biasin the outcomes. Generally,
a quality assessment outside of a systematic review does not require evidence
synthesis method; however, it completely depends upon the utilization of evidence
synthesis method. The risk of bias assessment can be done by professionals who
may be conducted by the guideline development group or requires a
methodological expert or by experiences systematic review researchers.
·
Selection bias – Participant or Population comparability in a study
·
Performance bias – The influence of estimate effect (aspects other than the intervention
or exposure of interest)
·
Reporting bias – Problems with measurements or classification of outcome (missing
information)
The risk of bias is assessed frequently by evaluating the study
design and the conduct of the study because it is impossible to determine a
specific study has been affected by bias or not.
Different tools used to assess the risk of bias in the systematic review:
AMSTAR 2 - A MeaSurementTool to Assess
systematic Reviews
AHRQ RRB - AHRQ tool for evaluating the Risk of
Reporting Bias
AHRQ ORB – AHRQ Outcome and analysis Reporting
Bias framework
GRADE-CERQual – GRADE Confidence in Evidence from
Reviews of Qualitative research
SAQAT – Semi-Automated Quality Assessment
Tool
NMA Quality – Framework for evaluating the quality
of evidence from a Network Meta-Analysis
NOS - Newcastle-Ottawa Scale
AXIS – Appraisal tool for Cross-Sectional
Studies
QUIPS - QUality In Prognosis Studies tool
RoB 2.0 - Revised tool for Assessing Risk of
Bias in randomized trials
SYRCLE RoB – SYstematic Review Centre for
Laboratory animal Experimentation Risk of Bias tool
ORBIT 2 - Outcome Reporting Bias In Trials
classification system for harm outcomes
Reid – Selective reporting bias algorithm
RTI 2012 – RTI Item Bank for Assessment of Risk
of Bias and Precision for Observational Studies of Interventions or Exposures
RTI 2013 – RTI Item Bank for Assessing Risk of
Bias and Confounding for Observational Studies of Interventions or Exposures
JBI - the Joanna Briggs Institute
OHAT - Office of Health Assessment and Translation
Downs Black - Downs Black tool
How to assess the risk of bias?
1.
Plan your approach
3.
Be aware of related issues
4.
Appraise each study
5.
Report the assessment process
6.
Use your appraisals to inform the
guideline
7.
In summary, risk of bias assessment is a tool used to regulate findings
which are accurate and appropriate, and it is essential to select the risk of
bias tool rightly. There are many researches available to help, and it makes
things easier to find appropriate tools for assessing the risk of bias.This
article describes different assessment tools for a systematic review and the types of study designs for which the tool is applicable along
with the flow of how to avoid the risk of bias.
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