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Dryad

Data for: Inter-rater reliability of risk of bias tools for non-randomized studies

Abstract

PURPOSE: Currently, there is limited knowledge about the reliability of risk of bias (ROB) tools for assessing internal validity in systematic reviews of exposure and frequency studies. We aimed to identify and then compare the inter-rater reliability (IRR) of six commonly used tools for frequency (Loney scale, Gyorkos checklist, American Academy of Neurology [AAN] tool) and exposure (Newcastle-Ottawa scale, SIGN50 checklist, AAN tool) studies.

METHODS: Six raters independently assessed the ROB of 30 frequency and 30 exposure studies using the 3 respective ROB tools. Articles were rated on a 3-level summary measure of ROB (low, intermediate, or high). We calculated an intraclass correlation coefficient (ICC) for each tool and category of ROB tool. We compared the IRR between ROB tools and tool type by inspection of overlapping ICC 95% CIs and by comparing their coefficients after transformation to Fisher Z values. We assessed criterion validity of the AAN ROB tools by calculating an ICC for each rater in comparison with the original ratings from the AAN.

RESULTS:  All individual ROB tools had an IRR in the substantial range or higher  (ICC point estimate = 0.61-0.80). The IRR was almost perfect (ICC point estimate > 0.80) for the AAN frequency tool and the SIGN50 checklist. All tools were comparable in IRR, except for the AAN frequency tool which had a significantly higher ICC than the Gyorkos checklist (p=0.021) and trended towards a higher ICC when compared to the Loney scale (p=0.085). When examined by category of ROB tool, scales and checklists had a substantial IRR, whereas the AAN tools had an almost perfect IRR. For the criterion validity of the AAN ROB tools, the average agreement between our raters and the original AAN ratings was moderate.

CONCLUSION: All tools had substantial IRR except for the AAN frequency tool and the SIGN50 checklist, which both had an almost perfect IRR. The AAN ROB tools were the only category of ROB tool to demonstrate an almost perfect IRR. This category of ROB tool had fewer and more simple criteria. Overall, parsimonious tools with clear instructions, such as those from the AAN, may provide more reliable ROB assessments.