2.1.3 Appraisal of literature and systematic reviews

​​​​​​​​​​​A. Backgro​​​un​d & Definitions​​​​​​

Prior to initiating any study or experiment, it is highly recommended to conduct a thorough analysis of the literature. In order to make sure that there is no previously reported (animal or human) evidence that would trigger a revision in the study hypothesis, design or analysis.

For example; it may help to:

• justifiy the selection of experimental model(s) (including selection of experimental subjects, if applicable)
• justifiy the choice of controls (positive, negative, sham, etc.)
• justify the need of your study (presence of a gap of knowledge, and no unnecessary duplication of studies)
• justify the details regarding the intervention
• justify in case of a preclinical study that the outcomes selected are outcomes related to patient important outcomes
• estimate anticipated effect size(s) and support sample size calculations (see Section 2.1.6 - Sample size and power analysis​)

The conduct of a systematic review is a valuable tool to justify the design of your animal experiment.

A systematic review (SR) is a literature review that aims to identify, select, appraise and synthesize all relevant studies to answer a specific research question (de Vries et al. 2014)​.

SR follows a series of standard steps that are determined a priori and described in a protocol (de Vries et al. 2014).

The conduct of a full SR before starting a new animal experiment may not always be feasible, however, a comprehensive thorough analyses of the literature is feasible and strongly recommended.

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B. Gu​​​idance &​ Expectations

A thorough analyses of the literature may or may not be in the form of a systematic review but it is recommended to develop and document the key steps of the review.

A systematic review of animal studies is comprised of seven main steps:

1. Phrase the preclinical research question (Hooijmans et al. 2018; Leenaars et al. 2012)
2. Search for all evidence related to this question (Leenaars et al. 2012)
3. Select the relevant animal/preclinical studies (Leenaars et al. 2012)
4. Extract study data (characteristics and outcome data)
5. Assess the study quality (Macleod et al. 2004; Hooijmans et al. 2014)
6. Synthesize the data (and if possible, perform a meta-analysis) (Vesterinen et al. 2014; Hooijmans et al. 2014​)
7. Interpret your results. (Hooijmans et al. 2018)

If a systematic review is performed, it is recommended to follow the guidance for its conduct, reporting, and critical appraisal.

For a thorough analysis of the literature, it is recommended at least to:

• phrase a preclinical research question
• conduct a comprehensive search
• qualitatively synthesize the results

Together with a study plan, a thorough appraisal of literature can be disclosed prior to the study in a form of a pre-registered report (see Section 2.1.11 - Preregistration​).

​PLEASE DO NOT FORGET

​To consider adding this subject to a training program for new employees or refresher training (if appropriate) To check whether there are feedback channels installed so that your colleagues can identify, record and report errors and critical incidents related to this subject​ (if appropriate)​

C. Resources

• ​​​de V​ries RB, Wever KE, Avey MT et al (2014) The usefulness of systematic reviews of animal experiments for the design of preclinical and clinical studies. ILAR J 55:427-437. PubMed​ ​
• Sena ES, Cu​rrie GL, McCann SK​. et al (2014) Systematic reviews and meta-analysis of preclinical studies: why perform them and how to appraise them critically. J Cereb Blood Flow Metab 34:737-742. PubMed
• Leenaars M, Hooijmans CR, van Veggel N et al (2012) A step-by-step guide to systematically identify all relevant animal studies. Laboratory Animals 46:24–31. PubMed
• Vesterinen HM, Sena ES, Egan KJ et al (2014) Meta-analysis of data from animal studies: A practical guide. J Neurosci Methods 221:92-102. PubMed​

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