PRISMA 2020 is the current reporting standard for systematic reviews and meta-analyses, published by Page and colleagues in the BMJ in March 2021. It is a 27-item checklist across seven manuscript sections, a structured abstract checklist, and a revised four-phase flow diagram. It replaces the 2009 statement, which should no longer be used for new reviews.
Understanding PRISMA correctly is the difference between meeting it and performing it. Most authors know PRISMA exists. Fewer understand exactly what it requires at every section, which items generate the most reviewer objections, what the flow diagram must contain, or how PRISMA-P, PRISMA-ScR, and the other extensions change the requirements for different review types. This guide covers all of it.
Quick answer:
PRISMA 2020 is a 27-item reporting checklist across seven sections (title, abstract, introduction, methods, results, discussion, and other information), a four-phase flow diagram, and a structured abstract checklist. It tells you what to report, not how to conduct the review. PRISMA-P is the separate 17-item protocol version. PRISMA-ScR is an extension of PRISMA for scoping reviews. A manuscript submitted to most biomedical journals is expected to include a completed PRISMA 2020 checklist as a supplementary file.
What PRISMA 2020 is and what it is not
PRISMA stands for Preferred Reporting Items for Systematic reviews and Meta-Analyses. The 2020 version is a reporting guideline, meaning it specifies what information a systematic review manuscript must contain to allow readers to understand what was done, assess the risk of bias, and replicate the process. It is not a tool for conducting the review, a search strategy, a risk-of-bias instrument, or a quality assessment for the included studies. A review can follow PRISMA 2020 precisely and still be methodologically weak, just as a methodologically excellent review can fail to meet PRISMA reporting standards. They address different things.
PRISMA 2020 is endorsed by the EQUATOR Network, which coordinates health research reporting guidelines. Most leading biomedical journals now require a completed PRISMA checklist as a submission requirement, either as a supplementary file or embedded in the manuscript. Some journals additionally require PRISMA-S, the extension for detailed search-strategy reporting.
What changed from PRISMA 2009
The 2020 update retains 27 items, the same count as the 2009 version, but the content, structure, and specificity have changed substantially. The following are the most consequential changes for authors submitting today.
Full reproducible search strategies are now explicitly required. The 2009 version mentioned search strategies; the 2020 version requires them to be reported in full for at least one database, with enough detail that another researcher could reproduce the search. The PRISMA-S extension provides additional guidance on search reporting and is increasingly expected by methods-oriented journals.
The flow diagram was redesigned. The 2020 flow diagram separates the identification stage into distinct pathways: one for records retrieved from databases and registers, and one for records identified through other methods such as citation searching, grey literature, and expert contact. The 2009 version had a single identification pathway. The new version also separates studies included in the review from the number of reports associated with those studies, reflecting the reality that a single study may have multiple associated reports.
Automation tool use must be reported. Where any part of the process, including screening, data extraction, or risk of bias assessment, was assisted by software or machine-learning tools, the 2020 checklist requires this to be declared.
The abstract checklist is now integrated. In 2009, a structured abstract checklist was published as a separate extension. The 2020 update incorporates it directly.
Certainty of evidence is explicitly covered. The methods section now includes an item for how certainty of evidence was assessed, typically with GRADE, and the results section requires that certainty ratings be reported per outcome.
Competing interests and data availability must be provided. These are captured in the new Other Information section.
The Protocol and registration item moved. In the 2009 checklist, this appeared at the start of the Methods section. In the 2020 checklist, it has been moved to the Other Information section, with a sub-item for amendments.
The 27 items section by section
Table 1: PRISMA 2020 checklist showing all 27 items distributed across 7 manuscript sections from title through other information.
The PRISMA 2020 checklist is structured to follow the natural layout of a manuscript, making it double as a writing guide. [See table image: PRISMA 2020 Sections Overview]
Title (1 item). The report must be identified as a systematic review and, if applicable, as including a meta-analysis. The title should not only describe the topic but also explicitly name the review type so readers and databases can correctly classify the work.
Abstract (1 item). A structured summary following the PRISMA 2020 for Abstracts checklist: background, objectives, eligibility criteria, information sources, risk of bias methods, results including the number of studies and participants, limitations, conclusions, and the registration number. This is where many authors fail without realizing it, by writing a general summary rather than a structured one that captures each required element.
Introduction (2 items). Item 3 is the rationale: why this review is needed, what gap it addresses, and how it builds on existing evidence. Item 4 is the objectives: the precise question the review addresses, ideally framed using PICO or PECO.
Methods (11 items). This is the most detailed section of the checklist and the one reviewed most carefully by methodological peer reviewers. The 11 items cover eligibility criteria and the PICO or PECO framework; all information sources searched including databases, registers, and grey literature, with dates; the full search strategy for at least one database; the selection process including how many reviewers screened independently and how disagreements were resolved; the data-collection process including the number of reviewers and any automation tools; all data items sought including outcomes, participant characteristics, and funding; the risk of bias assessment including the tool used and how many reviewers assessed each study; effect measures; synthesis methods including heterogeneity assessment and the rationale for the chosen model; reporting bias assessment methods; and certainty-of-evidence assessment methods.
Results (8 items). Covers the study selection process with the PRISMA flow diagram; characteristics of included studies; risk of bias in each included study; results of individual studies, including effect estimates and precision; results of syntheses, including pooled estimates and heterogeneity; assessment of reporting biases; and certainty of evidence per outcome.
Discussion (4 items). A general interpretation of results in context; limitations of the evidence and the review process; implications for practice, policy, and future research; and conclusions.
Other information (3 items). Registration details and where the protocol can be accessed, with any amendments disclosed; funding sources and the role of funders; and competing interests of all review authors.
The PRISMA 2020 flow diagram
The flow diagram is one of the most scrutinized elements in submissions because it serves as the visual audit trail of the selection process. Reviewers check it for logical consistency with the numbers in the methods and results sections, and discrepancies between the flow diagram and the manuscript text are a common reason for revision requests.
The 2020 flow diagram has four phases and, for original reviews, two parallel pathways in the identification phase.
Identification records the total number of records retrieved from databases and registers in the left column, and the total from other methods (citation searching, grey literature, contacting authors, reviewing reference lists) in the right column. Both columns must show how many duplicate records were removed, how many records were excluded before screening, and how many records were identified for screening.
Screening shows how many records were screened, how many were excluded and on what grounds, how many reports were sought for retrieval, how many could not be retrieved, and how many reports were assessed for full-text eligibility.
Eligibility shows how many reports were excluded at the full-text stage and the specific reason for each exclusion group. Listing exclusion reasons with numbers is an explicit requirement of the 2020 update.
Included shows the final count of studies included in the review and, separately, the number of reports of those studies. If a meta-analysis was performed, the number of studies and participants included in each analysis should be reported in the results section.
The reconciled numbers across all four phases must be internally consistent. A common error is reporting different total counts for the same stage in the flow diagram versus the manuscript text. Reviewers notice this immediately.
PRISMA-P for protocols
PRISMA-P is the separate reporting standard for systematic review protocols, published by Shamseer and colleagues in the BMJ in 2015. It contains 17 items covering the administrative information, introduction, and methods sections of a protocol document. Registering a protocol on PROSPERO and then reporting it against PRISMA-P provides a complete, checkable record of what was planned before any searching began.
The distinction between PRISMA-P and PRISMA 2020 matters at submission: some journals ask for the PRISMA 2020 checklist alongside the PRISMA-P protocol as separate documents, and submitting the wrong one for each document is an avoidable error.
The PRISMA extension family
PRISMA 2020 is the core standard. A suite of extensions covers specific review types and reporting needs.
PRISMA-ScR (Tricco and colleagues, Annals of Internal Medicine, 2018) is the 20-item extension for scoping reviews, which have different reporting requirements because critical appraisal is optional and the synthesis is descriptive.
PRISMA-S provides detailed guidance on reporting literature searches, covering 16 elements including the full search strings, the date of each search, and any limits applied. Methods-focused journals are increasingly asking for PRISMA-S compliance.
PRISMA-NMA covers network meta-analyses, in which treatments that have not been compared head-to-head are connected via indirect comparisons.
PRISMA-IPD covers systematic reviews using individual participant data rather than published summary statistics.
PRISMA-Harms covers the reporting of adverse events data in systematic reviews.
The EQUATOR Network maintains the full list of active PRISMA extensions and their status.
Common reporting errors reviewers flag
The 2019 survey of librarian methodological peer reviewers, published in Research Integrity and Peer Review, found that the most common bases for recommending rejection or revision were the search methodology and the search write-up, both of which are PRISMA items. The flow diagram is the second most scrutinized element after the search. The following errors recur across submissions.
Incomplete search reporting. The full search string for at least one database must be included, either in the methods section or as a supplement. A narrative description of the databases searched, without the actual search terms, fails PRISMA item 7 and is a reliable trigger for reviewer objection.
Flow diagram numbers that do not reconcile. The total records identified, the numbers excluded at screening, the numbers excluded at full-text, and the final included count must be consistent between the flow diagram and every table or statement in the manuscript. A one-number discrepancy undermines confidence in the whole count.
Using a single identification pathway. The 2020 flow diagram requires a separate pathway for records from other methods. Authors using the 2009 template with a single identification column are reporting against the superseded standard.
Missing exclusion reasons at the full-text stage. The 2020 checklist requires that the reasons for full-text exclusion be reported, along with the number excluded for each reason, rather than simply the total excluded.
Unchecked or inaccurate checklist. Submitting a checklist with all items marked as addressed, but without filling in the page and line numbers, tells reviewers it has not been completed properly. Fill in the location for every item.
Reporting certainty without GRADE. The 2020 checklist includes an explicit item for certainty-of-evidence assessment per outcome. Describing results without a certainty rating fails item 15 in methods and the corresponding results item.
Confusing PRISMA with PRISMA-P. The protocol checklist and the final review checklist are separate documents. Submitting PRISMA-P where PRISMA 2020 is required, or vice versa, causes immediate confusion at the editorial stage.
A pre-submission PRISMA audit
Before submission, run the manuscript against this list:
The title explicitly identifies the work as a systematic review or systematic review and meta-analysis.
The abstract follows the PRISMA 2020 for Abstracts structured format and includes the registration number.
The rationale states what gap this review addresses and why a new review is warranted.
The objectives use a structured question framework (PICO or PECO).
The full search string for at least one database is included verbatim in the manuscript or supplement.
The flow diagram uses the 2020 template with separate identification pathways for database/register records and other-source records.
Flow diagram numbers reconcile with every count in the methods and results text.
Full-text exclusion reasons are listed with counts.
Risk of bias is reported at the result level, not just the study level.
Certainty of evidence is rated and reported per outcome.
Competing interests and funding sources are declared.
A completed PRISMA checklist with page and line numbers is attached as a supplementary file.
Frequently asked questions
Is PRISMA 2020 mandatory?
Most major biomedical and health journals require a PRISMA checklist as part of the submission. It is not a legal requirement, but submitting to a journal that requires it without one usually results in a desk rejection or an immediate revision request before review begins.
Can I still use PRISMA 2009?
No. The 2020 statement explicitly replaces the 2009 version. The PRISMA 2020 authors state that the 2009 statement should no longer be used for new reviews. Reviewers and editors familiar with the updated standard will immediately identify old templates.
Does PRISMA apply to scoping reviews?
Not directly. Scoping reviews are reported using PRISMA-ScR, the dedicated 20-item extension published by Tricco and colleagues in 2018. PRISMA 2020 applies to systematic reviews and meta-analyses.
Where do I get the official PRISMA 2020 checklist?
The checklist, the expanded explanatory checklist, the flow diagram templates, and all extensions are freely available at prisma-statement.org and through the EQUATOR Network at equator-network.org.
What is the difference between PRISMA 2020 and PRISMA-P?
PRISMA 2020 is completed for the final review manuscript. PRISMA-P (Shamseer and colleagues, BMJ, 2015) is the 17-item checklist completed for the protocol, before any searching begins. Both may be submitted to a journal at different stages of the review process.
Does PRISMA 2020 cover updated systematic reviews?
Yes. PRISMA 2020 includes a separate flow diagram template for updated reviews, which shows where newly identified studies entered the search, screening, and inclusion process relative to the previous version of the review.
Meeting the standard from the start
PRISMA 2020 compliance is not an afterthought to tack on at the end of the writing. The most effective way to meet it is to plan for every item during the protocol stage: define the data items, pre-specify the synthesis approach, choose a risk-of-bias tool, and confirm that the flow diagram structure matches how screening was actually conducted. By the time the manuscript is drafted, every item should already have its location in the text.
If your review is in draft and you want an experienced systematic review specialist to audit it against PRISMA 2020 before you submit, ScribeLab Writer works with researchers preparing systematic reviews and meta-analyses for Tier 1 and Tier 2 journals. A pre-submission PRISMA audit removes a whole category of avoidable reviewer objections.
