A comparison of two assessment tools used in overviews of systematic reviews: ROBIS versus AMSTAR-2

BACKGROUND: AMSTAR-2 is a 16-item assessment tool to check the quality of a systematic review and establish whether the most important elements are reported. ROBIS is another assessment tool which was designed to evaluate the level of bias present within a systematic review. Our objective was to compare, contrast and establish both inter-rater reliability and usability of both tools as part of two overviews of systematic reviews. Strictly speaking, one tool assesses methodological quality (AMSTAR-2) and the other assesses risk of bias (ROBIS), but there is considerable overlap between the tools in terms of the signalling questions. METHODS: Three reviewers independently assessed 31 systematic reviews using both tools. The inter-rater reliability of all sub-sections using each instrument (AMSTAR-2 and ROBIS) was calculated using Gwet’s agreement coefficient (AC(1) for unweighted analysis and AC(2) for weighted analysis). RESULTS: Thirty-one systematic reviews were included. For AMSTAR-2, the median agreement for all questions was 0.61. Eight of the 16 AMSTAR-2 questions had substantial agreement or higher (> 0.61). For ROBIS, the median agreement for all questions was also 0.61. Eleven of the 24 ROBIS questions had substantial agreement or higher. CONCLUSION: ROBIS is an effective tool for assessing risk of bias in systematic reviews and AMSTAR-2 is an effective tool at assessing quality. The median agreement between raters for both tools was identical (0.61). Reviews that included a meta-analysis were easier to rate with ROBIS; however, further developmental work could improve its use in reviews without a formal synthesis. AMSTAR-2 was more straightforward to use; however, more response options would be beneficial.