Newcastle–Ottawa scale

In statistics, the Newcastle–Ottawa scale is a tool used for assessing the quality of non-randomized studies included in a systematic review and/or meta-analyses. Using the tool, each study is judged on eight items, categorized into three groups: the selection of the study groups; the comparability of the groups; and the ascertainment of either the exposure or outcome of interest for case-control or cohort studies respectively. Stars awarded for each quality item serve as a quick visual assessment. Stars are awarded such that the highest quality studies are awarded up to nine stars. The method was developed as a collaboration between the University of Newcastle, Australia, and the University of Ottawa, Canada, using a Delphi process to define variables for data extraction. The scale was then tested on systematic reviews and further refined.[1] Separate tools were developed for cohort and case–control studies. It has also been adapted for prevalence studies.[2][3][4]