PRISMA 2020 is the reporting standard for systematic reviews and meta-analyses. The statement, developed by the PRISMA Group, helps authors to transparently present the search, selection, appraisal, and synthesis of studies in a review. The version includes a checklist, an extended checklist, and flow diagrams for new and updated reviews.
Scope of Systematic Reviews
PRISMA 2020 applies to studies that systematically identify and assess evidence based on a pre-defined question. This can be a systematic review with or without a quantitative meta-analysis. The standard addresses the entire report: title, abstract, introduction, methods, results, discussion, and additional information on funding or conflicts of interest.
The 2020 version was published in 2021, among others, in the BMJ. Its 27 items cover not only the presentation of results but also information sources, search strategy, study selection, and assessment of bias risk. The available flow diagrams differentiate between a newly created and an updated review.
Report on Search and Evidence Synthesis
The PRISMA report must show how the authors progressed from a research question to the included evidence. This includes inclusion criteria, all information sources searched, complete search strategies, and the procedure for selecting hits. For exclusions after full-text screening, the reasons must be reported in a way that makes the selection process transparent.
If results are quantitatively combined, PRISMA describes the synthesis and the methods used for it. It also requires the presentation of individual study results, the assessment of potential biases, and the limitations of the evidence base. The checklist does not decide whether a meta-analysis is substantively justifiable; however, it makes visible the steps by which a published synthesis was achieved.
Distinction: Reporting, Not Synthesis Method
PRISMA 2020 is not a methods manual for conducting a systematic search or a meta-analysis. It does not prescribe databases, a statistical model, a heterogeneity measure, or a specific effect metric. Such methodological decisions are part of review planning and must align with the research question and the data material.
The term meta-analysis refers to the quantitative summary of study results; a literature review or an evidence synthesis can refer to other forms of processing. PRISMA 2020 is the overarching reporting framework that organizes information about these decisions in systematic reviews and meta-analyses. Publication bias, in turn, is a potential problem of the existing evidence, not an alternative name for the guideline.
The checklist also distinguishes between the previously planned procedure and the steps actually applied. Changes to inclusion criteria, information sources, or synthesis methods are not per se impermissible but must be identifiable as changes. When updating a review, it is also important to note which studies were already examined in the previous version and which were added with the new search. This allows the knowledge status of a review to be contextualized in time.
PRISMA 2020 is also aimed at editors and reviewers who need to assess whether a review is sufficiently described. The checklist can be used as a control instrument before submission, without replacing the independent evaluation of search quality. It particularly helps to make the distinction between pre-planned search, post-hoc decisions, and actually included evidence visible in the manuscript.
The standard is not only suitable for drug efficacy. Systematic reviews can investigate diagnostic procedures, safety issues, healthcare interventions, or methodological topics. The specific research question determines which study types and results are included. PRISMA requires a clear presentation of the selection and synthesis steps even if the included evidence is so heterogeneous that only a structured narrative summary, rather than a pooled effect calculation, is possible.
Relevance for clinical trials
Systematic reviews influence the justification of new studies, the choice of comparator therapies, and the interpretation of individual study results. If search strings, exclusion reasons, or the separate presentation of included studies are missing, it is often impossible to assess whether an evidence gap truly exists. For clinical development programs, PRISMA documents are therefore particularly relevant when literature data support a study rationale or a benefit-risk argument.
Full-service CROs like Mediconomics support PRISMA 2020 projects through planning reproducible literature searches, screening according to pre-defined criteria, and structured data extraction. Biostatistics can review the key figures and sensitivity analyses intended for a meta-analysis, while Medical Writing integrates the flow diagram, results presentation, and checklist into the review report. For an HTA dossier, search protocols and evidence tables can thus be transferred into an auditable documentation line.
Frequently Asked Questions (FAQ)
Does PRISMA 2020 always require a meta-analysis?
No. The standard applies to systematic reviews; a quantitative summary is only one possible form of evidence synthesis.
What is the purpose of the PRISMA flow diagram?
It shows how many records were identified, screened, assessed for eligibility via full-text, excluded, and finally included in the review.
Is a narrative literature review automatically PRISMA-compliant?
No. The decisive factor is not the designation, but whether the work is designed as a systematic review and reported according to the relevant PRISMA specifications.
Regulatory References
- PRISMA 2020 Statement — Defines the reporting framework for systematic reviews.
- PRISMA 2020 Explanation and Elaboration — Specifies the checklist items with explanations.
- PRISMA 2020 Flow Diagrams — Provides templates for new and updated reviews.
- ICMJE Recommendations — Names PRISMA as a reporting guideline for systematic reviews and meta-analyses.