From finding evidence to making sense of it

Toxicology is increasingly becoming an evidence-integration discipline.

Questions about chemical safety, mechanisms of toxicity, alternative methods, exposure, risk assessment and regulatory decisions rarely depend on a single study or evidence type. Instead, toxicologists may need to integrate findings from in vivo studies, in vitro assays, epidemiology, mechanistic research, exposure data, computational methods and the broader scientific literature.

This makes systematic and other forms of evidence synthesis increasingly important.

Two resources stand out as useful starting points for toxicologists who want to strengthen these skills:

• the World Health Organization (WHO) Training Package for Systematic Reviews
• the JBI Manual for Evidence Synthesis

Together, they provide both accessible training and detailed methodological guidance.

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1. WHO Training Package for Systematic Reviews

The WHO Regional Office for the Eastern Mediterranean has developed a Training Package for Systematic Reviews designed to help researchers understand and apply evidence-synthesis methods.

WHO describes systematic reviews as one of the most rigorous and transparent approaches to synthesising literature and provides resources covering both systematic reviews and other synthesis methodologies.

The package starts with the fundamentals:

• understanding different evidence-synthesis designs
• developing a focused review question
• understanding the steps involved in conducting a systematic review
• understanding principles for ethical evidence generation

It then provides a selection of courses and resources from organisations including Cochrane, WHO/PAHO, Campbell Collaboration and UNICEF.

Some particularly useful resources include:

Introduction to Conducting Systematic Reviews — Cochrane
A one-hour introductory course covering the basic steps of a systematic review.

Systematic Reviews of the Literature — WHO/PAHO
A 20-hour introductory course covering the systematic review process in greater depth.

Systematic Reviews and Meta-Analysis — Campbell Collaboration
An open course introducing quantitative systematic review and meta-analysis.

Introduction to Qualitative Evidence Synthesis — Cochrane
An introduction to approaches for synthesising qualitative evidence.

For researchers wanting to progress further, WHO also points to resources on meta-analysis, statistical methods, critical appraisal, GRADE, literature searching and living systematic reviews.

Explore the WHO training package:
WHO Training Package for Systematic Reviews

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2. JBI Manual for Evidence Synthesis

While the WHO package is particularly useful as a learning pathway, the JBI Manual for Evidence Synthesis provides a much more detailed methodological reference.

The JBI Manual recognises that evidence synthesis is part of a broader “evidence ecosystem” and that different research questions require different synthesis approaches.

This is particularly relevant to toxicology.

Not every toxicological question can—or should—be addressed through a conventional effectiveness review or meta-analysis.

JBI provides guidance across a broad range of approaches, including:

• systematic reviews of effectiveness
• systematic reviews of qualitative evidence
• systematic reviews of etiology and risk
• systematic reviews of diagnostic test accuracy
• systematic reviews of prevalence and incidence
• mixed-methods systematic reviews
• umbrella reviews
• scoping reviews
• reviews of textual evidence
• reviews of economic evidence

The Manual also provides detailed guidance on protocol development, searching, study selection, critical appraisal, data extraction, synthesis and meta-analysis.

Explore the JBI Manual:
JBI Manual for Evidence Synthesis

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Why does this matter for toxicologists?

The value of systematic review methodology for toxicology goes beyond simply producing a better literature review.

A rigorous evidence-synthesis approach can help toxicologists:

Find evidence systematically rather than relying on ad hoc searches.

Evaluate evidence critically by considering methodological quality, relevance and potential bias.

Integrate different evidence streams in a transparent and reproducible way.

Identify knowledge gaps and uncertainties that may otherwise remain hidden within a large body of literature.

Support regulatory and scientific decisions with a more structured assessment of the available evidence.

This becomes particularly important as toxicology moves toward approaches that integrate traditional and new approach methodologies (NAMs), mechanistic evidence, computational predictions and human-relevant data.

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Systematic review ≠ one-size-fits-all

One of the most important lessons from these resources is that evidence synthesis is not a single methodology.

The appropriate approach depends on the question.

A broad question about what evidence exists in a particular field may call for a scoping review.

A question about whether an exposure is associated with a particular outcome may require a review of etiology and risk.

A question involving several different types of evidence may benefit from a mixed-methods approach.

And when multiple systematic reviews already exist, an umbrella review may be more appropriate.

This methodological flexibility is particularly relevant to toxicology, where scientific questions can span very different evidence types and study designs.

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From evidence synthesis to evidence integration

For toxicologists, the ultimate objective should not simply be to produce more systematic reviews.

The bigger challenge is to turn fragmented evidence into useful knowledge.

That means connecting:

Evidence → Critical appraisal → Integration → Interpretation → Decision-making

This is where systematic review methodology becomes particularly valuable.

It provides a structured foundation for understanding what we know, how confidently we know it, what remains uncertain, and what evidence is still needed.

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Building evidence-synthesis skills within toxicology

At TOXICOLOGIST, we believe that strengthening these skills can contribute to a more transparent, interdisciplinary and evidence-driven toxicology community.

Systematic reviews, critical appraisal and evidence integration are not isolated research techniques. They are part of a broader skill set that can help toxicologists navigate an increasingly complex evidence landscape.

For toxicologists looking to develop these capabilities, the WHO training package is an excellent starting point, while the JBI Manual provides a valuable methodological reference when planning or conducting more advanced evidence syntheses.

Together, they are worth bookmarking.

Useful resources

WHO — Training Package for Systematic Reviews
Access the WHO training package

JBI — Manual for Evidence Synthesis
Access the JBI Manual