A systematic review guideline 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 bias in 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. Once the evaluation is done, then it can be used for the synthesis of study results and findings and combined into the complete assessment of the evidence. There are certain common factors which can introduce bias in many research areas, that include
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:
How to assess the risk of bias?
Determining an appropriate risk of bias assessment tool:
|Study type||Assessment tools||Year||Source|
|Systematic reviews||AMSTAR – 2||2017||https://amstar.ca/Amstar-2.php|
|Randomized trials||Cochrane RoB 2.0 Tool||2016||www.riskofbias.info|
|Non-randomised studies of interventions (case-control, cohort, etc.)||ROBINS-I||2016||www.riskofbias.info|
|Prognostic: Prognostic factorsRisk prediction modellingOverall prognosis/baseline risk/prevalence/incidence||JBI checklist for prevalence studies||2017||http://joannabriggs.org/research/critical-appraisal-tools.html|
|Qualitative||CASP Qualitative Checklist||2018||https://casp-uk.net/wp-content/uploads/2018/01/CASP-Qualitative-Checklist-2018.pdf|
|JBI Checklist for Qualitative Research||2017||http://joannabriggs.org/research/critical-appraisal-tools.html|
|Observational studies of exposures (human epidemiology, wildlife)||Navigation Guide risk of bias checklist||2018||https://www.cosmin.nl/|
|In vivo animal studies||Navigation Guide risk of bias checklist||2018||https://www.cosmin.nl/|
|SYRCLE tool||2014||Systematic Review Centre for Laboratory Animal Experimentation|
|In vitro studies||OHAT tool||2015||https://ntp.niehs.nih.gov/ntp/ohat/pubs/riskofbiastool_508.pdf|
|Obtained from: https://www.nhmrc.gov.au/guidelinesforguidelines/develop/assessing-risk-bias#|
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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