PRISMA Guidelines: Why Transparency Matters in Evidence Synthesis

In evidence-based medicine, how you arrive at a conclusion is just as important as the conclusion itself. Health technology assessment (HTA) agencies, regulators, and peer-reviewed journals are no longer satisfied with evidence summaries that only present results — they want to know exactly how the evidence was identified, screened, and synthesized.

That’s where the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) play a vital role.

Originally developed in 2009 and updated in 2020, PRISMA provides a structured framework for reporting systematic reviews and meta-analyses. It emphasizes transparency, reproducibility, and accountability, making it indispensable for literature reviews used in HTA submissions, global value dossiers (GVDs), and regulatory reports.

In this blog, we’ll explore:

• Why PRISMA compliance matters

• The core elements of PRISMA

• The risks of ignoring it

• A real-world case study of how PRISMA saved a company’s HTA submission

• Best practices to embed PRISMA into evidence synthesis strategies

🔹 Why Transparency Matters in Evidence Synthesis

Evidence synthesis is not just about collecting studies. It is about demonstrating that the search for evidence was comprehensive, unbiased, and systematic. Without clear methodology, reviewers may suspect selective reporting or cherry-picking — even if that wasn’t the case.

Transparency builds trust. When reviewers at NICE, CADTH, PBAC, or the FDA see a PRISMA-compliant review, they know:

• The evidence base is complete and unbiased

• Methods are reproducible and auditable

• Excluded studies were omitted for documented, justifiable reasons

This credibility can be the difference between a smooth submission and one riddled with delays or objections.

🔹 Key Components of PRISMA

The PRISMA 2020 Statement outlines 27 checklist items and an updated flow diagram. While detailed, the essentials can be grouped into four domains:

1. Search Transparency

   • Full reporting of databases, keywords, Boolean logic, filters, and date ranges.

2. Screening Process

   • Clear inclusion/exclusion criteria.

   • Documented number of studies at each stage of screening.

3. Flow Diagram

   • Visual summary of how many records were identified, screened, excluded, and included.

4. Results and Synthesis

   • Transparent presentation of study characteristics, risk of bias, and narrative or statistical synthesis.

Together, these elements create a blueprint of reproducibility — a roadmap that others can follow to replicate the review.

🔹 The Risks of Skipping PRISMA

When PRISMA guidelines are ignored, the consequences can be serious:

• HTA Pushback: Agencies may challenge the validity of the evidence base, request additional analyses, or even reject submissions.

• Regulatory Delays: Incomplete documentation can lead to deficiency letters or resubmission requirements.

• Payer Skepticism: Lack of transparency undermines confidence in value dossiers and payer slide decks.

• Wasted Effort: Reviews that aren’t PRISMA-compliant often need to be redone from scratch, costing time and resources.

In short, non-compliance creates doubt — and doubt delays decisions.

🔹 Case Study: PRISMA in Action

Case Study: How a PRISMA-Compliant Literature Review Helped Secure HTA Acceptance

The Challenge

A mid-sized biotech company preparing a Health Technology Assessment (HTA) submission for an immunology therapy faced a critical problem.

Their commissioned literature review lacked transparency:

• No PRISMA flow diagram

• Vague search strategy documentation

• No rationale for included/excluded studies

• Tables of results with no clear methodological link

The internal team feared that HTA reviewers (particularly NICE and CADTH) would flag the review as biased or incomplete — potentially leading to resubmission requests and 3–6 months of delays.

Our Approach: Rebuilding the Review with PRISMA

We restructured the review according to PRISMA 2020 standards:

1️⃣ Protocol Development

• Reframed objectives using PICO (Population, Intervention, Comparator, Outcomes).

• Outlined clear inclusion/exclusion criteria and review scope.

2️⃣ Search Strategy Documentation

• Re-ran comprehensive searches across Medline, Embase, CENTRAL, and grey literature.

• Reported keywords, MeSH/Emtree terms, Boolean logic, and filters in full detail.

3️⃣ Screening Transparency

• Applied dual-reviewer screening.

• Documented exclusions with reasons.

• Created a PRISMA flow diagram summarizing the process.

4️⃣ Quality Appraisal

• Used GRADE and NICE checklists to assess study validity.

• Classified evidence quality and incorporated it into synthesis.

5️⃣ Narrative Synthesis

• Synthesized results into clear themes, linked directly to included studies.

• Documented limitations and evidence gaps proactively.

The Results

✔️ HTA Success: The submission received no methodology-related objections. The PRISMA-compliant review was explicitly cited as a strength in the HTA report.

✔️ Stakeholder Confidence: The transparent flow diagram and screening logs reassured internal teams and external advisors.

✔️ Efficiency: Because of PRISMA compliance, the evidence package was easily adapted into a peer-reviewed manuscript, a Global Value Dossier annex, and payer slide decks.

✔️ Time Saved: By avoiding resubmission requests, the company likely saved 3–6 months in market access timelines.

📌 Key Takeaway from the Case PRISMA compliance transformed what could have been a weakness into a strength. Instead of facing delays, the company positioned its evidence as credible, defensible, and reusable across multiple deliverables.

🔹 Best Practices for Implementing PRISMA

Based on our experience, here’s how teams can embed PRISMA into their evidence workflows:

✅ Start with Protocols: Define your objectives and criteria before searching. 

✅ Document Everything: Capture search terms, filters, and databases for full transparency. 

✅ Use Dual Screening: Avoid bias by having two reviewers independently assess records. 

✅ Always Include a Flow Diagram: Visuals matter — HTA reviewers expect to see them. 

✅ Link Findings Back to Methods: Show how included studies map to your objectives. 

✅ Be Proactive About Limitations: Acknowledge gaps and propose mitigation plans.

🔚 Final Thoughts

The PRISMA guidelines are more than a compliance exercise — they are a strategic advantage. By embedding transparency and reproducibility into evidence synthesis, organizations can:

• Strengthen HTA submissions

• Build payer and regulator confidence

• Repurpose reviews across dossiers, manuscripts, and communication tools

• Avoid costly delays from weak methodology

In evidence synthesis, trust is everything — and PRISMA is how you earn it.

📌 Need help making your literature reviews PRISMA-compliant and HTA-ready? Our HEOR and medical writing experts design, execute, and document reviews with full PRISMA alignment — turning evidence into a strategic asset.

👉 [Contact us] to learn more or read our detailed Case Study on PRISMA Compliance in HTA Submissions.