Common tool structures and approaches to risk of bias assessment: implications for systematic reviewers

There are numerous tools available to assess the risk of bias in individual studies in a systematic review. These tools have different structures, including scales and checklists, which may or may not separate their items by domains. There are also various approaches and guides for the process, scoring, and interpretation of risk of bias assessments, such as value judgments, quality scores, and relative ranks. The objective of this commentary, which is part of the JBI Series on Risk of Bias, is to discuss some of the distinctions among different tool structures and approaches to risk of bias assessment and the implications of these approaches for systematic reviewers.