New guidelines for conducting systematic reviews of animal and cell studies

A new publication in Nature Reviews Methods Primers provides essential guidance for conducting rigorous systematic reviews on studies with animals and cells. It also highlights the benefits of these reviews, such as improving reproducibility and reducing animal use, and addresses potential pitfalls and recent advancements like review automation.

Systematic reviews synthesize existing evidence in a scientific field to answer specific research questions in a structured and unbiased way. With over 100 million animals used in scientific research annually and a deluge of publications to keep track of, the need for systematic reviews of animal research is more pressing than ever. Before initiating new studies, it's crucial to review the existing literature to avoid losing valuable time and resources. Regular narrative reviews are prone to biases, but systematic reviews follow a rigorous and transparent methodology, helping researchers make sense of conflicting reports and identify gaps in the field to focus on.

The Cochrane organization popularized systematic reviews and meta-analyses in clinical research. The first Cochrane Reviews Handbook, the gold-standard guide on performing systematic reviews, was published in 1994 and continues to be updated. For the last decade, researcher Kim Wever and colleagues from Radboud university medical center, along with collaborators from Switzerland and the UK, have been adapting this approach for animal studies that require different considerations. The new Nature Primer provides a comprehensive guide for the first time to perform systematic reviews of animal research and in vitro research using cells.

The article guides researchers throughout the whole process: defining the research question, writing and registering the protocol, conducting a literature search, selecting studies, critical assessment of evidence, data synthesis and drawing conclusions, ending up with reporting and publication. This process benefits the research, the researcher, and the animals. According to Wever, 'People realize, while doing the review, what types of animal models exist in their field, how they may refine these models, reduce the number of animals used, or even replace the animal model with an animal-free alternative. Looking at the literature through the lens of a systematic reviewer helps the quality of the research and its reporting'.

A global effort

The authors are part of the international collaboration CAMARADES (Collaborative Approach to Meta-Analysis and Review of Animal Experimental Studies). Wever and colleagues also run the PROSPERO4animals platform, where researchers can register their systematic review protocols and get expert feedback before starting the research.

We frequently encounter poor methodology and it's critical to amend it before the research is already done. Still, registration in PROSPERO is not mandatory, so I hope researchers will read the new article before they begin their systematic review."

Kim Wever, Researcher, Radboud University Medical Center

Funding for systematic reviews in the Netherlands

The Netherlands has a pioneering funding scheme to incentivize systematic reviews of animal studies and animal-free alternatives. With this fund from ZonMw (Netherlands Organization for Health Research and Development), researchers from Dutch institutions can receive 2 months of salary and up to 80 hours of expert supervision by Kim Wever and colleague Carlijn Hooijmans, also from Radboud university medical center. More information on this can be found on the ZonMw website.