Section 2 Preclinical Systematic Reviews

2.1 What is a systematic review?

A systematic review (SR) is a literature review that involves systematically locating, appraising, and synthesising evidence from scientific studies to answer a defined research question based on pre-specified criteria.

The methods of a systematic review (and meta-analysis) should be transparent and reproducible. This means that the methods are planned, conducted, and reported in a way that can be repeated by other research groups.

2.2 What is a meta-analysis?

A meta-analysis is a method of combining quantitative results from individual studies identified through systematic review in an overall statistical analysis.

2.3 Clinical & preclinical reviews

There are many differences between preclinical and clinical systematic reviews, which is why we developed this Wiki, specific to preclinical systematic review methodology.

	Preclinical	Clinical
# of included studies	High	Low
Sample size within studies	Low	High
Experimental design	Variable	Consistent
Uses	Investigate translational failure Explore differences between studies (heterogeneity) e.g. internal & external validity Inform future preclinical studies e.g. model selection Inform early phase clinical trials Explain discrepancies in preclinical vs. clinical trial results Inform 3Rs decisions	Explore heterogeneity e.g. clinical populations Inform later phase clinical studies Inform clinical practice and guidelines

2.4 Why perform preclinical SRs?

There are many reasons to perform preclinical systematic reviews:

To summarise evidence from multiple similar studies to allow for more accurate estimates of effect
The methods used to find and select studies are transparent and reproducible, reducing bias and increasing the likeliness of producing reliable and accurate conclusions.
Summarise findings from all available studies making information easier for the end-user to read and understand
Analyse individual study quality to inform confidence in the results
Quantitative synthesis of results (meta-analysis)
Allow for evidence-based inferences

The results of preclinical systematic reviews can:

Provide evidence to change research practice by identifying risks of bias in preclinical experiments
Influence development of reporting guidelines and editorial policies
Provide evidence to support reporting of positive, negative and neutral results through detection of publication bias
Identify study design features that compromise potential clinical application
Contribute to evidence-based clinical trial design