Fatal flaws in systematic review conduct, and how to fix them—A commentary to Rao. et al. (2022)

Abstract Systematic reviews are vital as robust summaries of research evidence for supporting evidence-informed decision-making in research, policy and practice. They are increasingly appreciated as valuable research outputs, but as the volume of so-called 'systematic reviews' increases in the literature, so too do pitfalls in the methodological approaches used. These pitfalls increase the risk of missing evidence but importantly also increase the risk of bias, and, in some cases, may result in inappropriate or incorrect conclusions. We were encouraged to see the recent review by Rao et al. (2022) on urban and peri-urban agriculture, but we identified a suite of methodological mistakes and unsuitable procedures that could be easily avoided with an awareness of freely available, Open Access methodological guidance. Here, we highlight what a systematic review (and systematic map) is, how they should be conducted, how Rao et al. (2022) fall foul of 17 common pitfalls in evidence synthesis methods and risk arriving at incorrect conclusions, and how these pitfalls can be avoided. Where standard methodological conduct and reporting guidance is not followed, systematic review conclusions may ignore important evidence or may be biased, and research, policy and practice recommendations may be wrong.