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Clin Epidemiol. 2014 Oct 10;6:359-68. doi: 10.2147/CLEP.S66677. eCollection 2014.

Quality assessment of observational studies in a drug-safety systematic review, comparison of two tools: the Newcastle-Ottawa Scale and the RTI item bank.

Author information

1
RTI Health Solutions, Barcelona, Spain.
2
Drug Safety Research Unit, Southampton, UK ; Associate Department of the School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK.
3
RTI International, Research Triangle Park, NC, USA.

Abstract

BACKGROUND:

The study objective was to compare the Newcastle-Ottawa Scale (NOS) and the RTI item bank (RTI-IB) and estimate interrater agreement using the RTI-IB within a systematic review on the cardiovascular safety of glucose-lowering drugs.

METHODS:

We tailored both tools and added four questions to the RTI-IB. Two reviewers assessed the quality of the 44 included studies with both tools, (independently for the RTI-IB) and agreed on which responses conveyed low, unclear, or high risk of bias. For each question in the RTI-IB (n=31), the observed interrater agreement was calculated as the percentage of studies given the same bias assessment by both reviewers; chance-adjusted interrater agreement was estimated with the first-order agreement coefficient (AC1) statistic.

RESULTS:

The NOS required less tailoring and was easier to use than the RTI-IB, but the RTI-IB produced a more thorough assessment. The RTI-IB includes most of the domains measured in the NOS. Median observed interrater agreement for the RTI-IB was 75% (25th percentile [p25] =61%; p75 =89%); median AC1 statistic was 0.64 (p25 =0.51; p75 =0.86).

CONCLUSION:

The RTI-IB facilitates a more complete quality assessment than the NOS but is more burdensome. The observed agreement and AC1 statistic in this study were higher than those reported by the RTI-IB's developers.

KEYWORDS:

AC1; meta-analysis; quality assessment; systematic review

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