Proposed Risk of Bias Assessment Tool for In Vitro Antimicrobial Susceptibility Studies

The assessment of risk of bias in systematic reviews and meta-analyses is crucial, as it indicates the accuracy of the synthesized and evaluated data and the validity of the presented results and conclusions. Until now, standardized tools for this purpose have been available only for clinical and animal studies, while adapted forms of these tools and novel ones have been proposed for in vitro and laboratory studies. However, none of them have been universally standardized so far. The apparent lack of a risk of bias assessment tool for systematic reviews of in vitro antimicrobial susceptibility testing studies constitutes a methodological flaw in these studies. To this end, we developed a risk of bias assessment tool for in vitro antimicrobial susceptibility testing studies. Our tool assesses the risk of bias across six domains: methodological bias, selection bias, preparation bias (including contamination/cross-contamination bias), measurement/observer bias, reporting and publication bias, and bias related to unreported funding and conflicts of interest. The tool evaluates a total of 16 specific criteria. The risk of bias is graded as low, moderate, or high for each evaluated criterion. The proposed risk of bias assessment tool was tested in a pilot validation study of ten relevant studies by two reviewers independently. We believe that the use of the proposed risk of bias assessment tool will increase the methodological strength of systematic reviews and meta-analyses of in vitro antimicrobial susceptibility testing studies.