Background: Assessing the quality of studies included in systematic reviews is an essential step. Assessing quality of observational studies in nutrition research is very challenging due to the type of methodological complexities. There is a lack of agreement on best-available tools to assess the quality of observational studies.
Objectives:Compare Academy of Nutrition and Dietetics Quality Criteria Checklist (QCC) and the Newcastle-Ottawa Scale (NOS) as risk-of-bias assessment tools for cohort studies within a systematic review.
Methods: This study compared the NOS and QCC risk-of-bias assessment tools for a systematic review of cohort studies. Eight cohort studies were included in the systematic review. Two reviewers individually reviewed all the 8 articles using QCC and NOS tool. The NOS contains 8 items that assess selection bias, comparability of groups, and assessment of exposure and outcomes. The QCC contain 9 validity questions focusing on selection bias, detection bias, performance bias, attrition bias, and reporting bias. An overall score was generated for each study based on the two tools.
Results:In step one, we mapped the individual questions for both the tools to Cochrane’s risk-of-bias domains (Selection, Attrition, Detection, Performance, other bias) and secondly, comparisons between the ratings for 2 tools for each domain were analysed. Mapping of each question for the 2 tools indicated that for the QCC tool questions were very well distributed across all the risk-of-bias domains (Selection domain: 2 questions; Performance domain: 2 questions; Detection domain: 2 questions; Reporting domain: 2 questions; Attrition domain: 1 question), whereas the NOS tool questions are more focused on selection-bias domain (Selection domain: 4 questions; Performance domain: 1 questions; Detection domain: 2 questions; Reporting domain: 0 questions; Attrition domain: 1 question). We are still in progress of calculating the inter-observer reliability status for both the tools.
Conclusions: QCC covers all domains of risk of bias, whereas NOS does not cover reporting bias and performance bias. Both the tools were easy to use.