PRISMA vs systematic review: what authors often confuse

You finish screening hundreds of papers, complete your PRISMA flow diagram, and write in the Methods section:

We conducted the review according to PRISMA.

The sentence sounds precise. It mixes a type of research with a reporting guideline.

A systematic review uses planned methods to find, select, evaluate, and combine evidence. PRISMA tells you how to report that process so readers can see what you did. You still have to choose the methods.

Systematic review = how the review is done.

PRISMA = how the review is reported.

That split changes the Methods sentence, and it changes what a reviewer can infer from a completed checklist.

Key takeaways

• A systematic review is the research: planned methods for finding, selecting, evaluating, and combining evidence.
• PRISMA is a reporting guideline. It asks you to describe those methods after you have already chosen them.
• A PRISMA flow diagram documents how records moved through screening. The numbers leave open whether the search, the eligibility rules, the bias assessment, or the synthesis were appropriate.
• Clear reporting can describe a weak search, and a careful search can still be written so vaguely that nobody can rerun it.
• Name both, separately: conduct the review using a method (for example Cochrane), and report it according to PRISMA 2020.

What is the difference between PRISMA and a systematic review?

PRISMA stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses. PRISMA 2020 supplies a 27-item checklist, an expanded checklist, guidance for abstracts, and flow diagrams, and its stated job is to help authors explain why the review was done, what they did, and what they found. A systematic review is the work itself: defining the question, setting eligibility criteria, searching, selecting studies, collecting data, assessing risk of bias, combining the findings, and interpreting the results. The Cochrane Handbook treats those as core methodological steps. PRISMA then asks you to report the decisions you made at each step.

Page and colleagues write that PRISMA 2020 “is not intended to guide systematic review conduct, for which comprehensive resources are available.” The checklist records the decisions behind the review. Handbooks and protocols are where those decisions get made.

What is a systematic review?

Page and colleagues define a systematic review as a review that uses explicit, systematic methods to collate and synthesise findings of studies that address a clearly formulated question. A long literature review can still leave the search, the eligibility rules, and the synthesis unplanned; what makes the work systematic is that those steps are decided in advance and then followed. The length of the reference list is a poor test of that.

Researchers usually lock down:

• what question the review will answer;
• which studies can be included;
• where and how they will search;
• how studies will be screened;
• what data will be collected;
• how risk of bias, meaning problems in a study that could affect its results, will be assessed;
• how the evidence will be combined and interpreted.

The Cochrane Handbook splits those activities into dedicated chapters, including scope and questions, inclusion criteria, searching and selecting studies, collecting data, risk of bias, preparing the evidence for synthesis, and interpreting the results. Together, those decisions are the review method, and they have to be in place before anyone fills in a reporting checklist.

What is PRISMA?

The original 2009 statement was written because systematic reviews were being reported incompletely, and PRISMA 2020 updates that guidance. The checklist asks authors to report the review objectives, eligibility criteria, information sources, search strategies, study-selection methods, data-collection methods, risk-of-bias assessment, synthesis methods, included studies, results, limitations, and registration or protocol information. Those items describe the decisions you already made. The official PRISMA 2020 resources include the 27-item checklist, the expanded checklist, an abstract checklist, and flow diagrams for new and updated reviews. Completing them records a database, an eligibility rule, a bias tool, and a synthesis model only after you have already chosen each one.

How should you describe the review in Methods?

Authors sometimes write:

We conducted a PRISMA systematic review.

or:

The study followed PRISMA methodology.

Those sentences treat PRISMA as the method used to conduct the review. A more precise sentence is:

We conducted a systematic review and reported it according to PRISMA 2020.

If you followed a specific methodological handbook, name that separately:

We conducted the systematic review using Cochrane methods and reported the review according to PRISMA 2020.

The phrase “PRISMA compliant” has the same problem. It can sound as if PRISMA confirmed the quality of the review. Write “The review was reported according to PRISMA 2020,” then describe the methods on their own terms.

A quick test: open the Methods paragraph that mentions PRISMA. Circle every phrase that names a method (Cochrane, JBI, a registered protocol, a named search strategy) and every phrase that names a reporting guideline (PRISMA 2020, PRISMA-S, PRISMA-ScR). If PRISMA is the only circled phrase, the paragraph is describing reporting as if it were conduct. Split it into two sentences.

What does the PRISMA flow diagram actually show?

For many authors, the flow diagram is the most familiar piece of PRISMA, which is why a completed figure gets treated as proof that the review was systematic. The diagram shows how records moved through the review: how many were identified, removed, screened, excluded, assessed, and finally included. A flow diagram can tell readers that you screened 1,200 records and included 34 studies, but those counts leave open whether the search covered appropriate databases, whether the search terms matched the question, whether inclusion criteria were applied consistently, whether risk of bias was assessed, and whether the synthesis method fit the evidence. The figure documents study selection. The methods that produced those counts still have to be judged on their own.

Can a review follow PRISMA and still use weak methods?

Imagine a review that searches only one database. The authors can report that fact in full, with dates, search strings, and a flow diagram, and the description can be transparent, yet transparency still leaves open whether one database was appropriate for the question. The same split applies to study selection, risk-of-bias assessment, and evidence synthesis: PRISMA helps readers see what the authors did, and once those methods are visible, readers can judge whether they were appropriate. PRISMA 2020 says the guideline should not be used to assess the conduct or methodological quality of systematic reviews; tools such as AMSTAR 2 exist for that job. A complete checklist can still describe a thin search, and a strong search can still be written so vaguely that readers cannot tell what was done.

Risk-of-bias assessment belongs to the method layer. The Cochrane Handbook has dedicated guidance on bias and on how to assess it. PRISMA then asks authors to report how they assessed risk of bias and what they found. The bias instrument is part of the method; PRISMA is the place where you name the tool you used and summarize the findings.

Does using PRISMA mean the review includes a meta-analysis?

The full name, Preferred Reporting Items for Systematic Reviews and Meta-Analyses, is easy to read as a requirement. A meta-analysis is a statistical method for combining quantitative results from multiple studies, while the systematic review is the broader process and can stop at a narrative synthesis or another non-statistical summary. PRISMA 2020 applies to systematic reviews that include statistical synthesis and to reviews that skip it, including cases where synthesis cannot be performed because only one eligible study is identified. Citing PRISMA leaves the reader still needing a description of the synthesis method, so report whether you performed a meta-analysis, a narrative synthesis, or no synthesis at all.

Who plans the search: the review method or PRISMA?

Which databases are relevant, which concepts belong in the strategy, which free-text terms and subject headings to use, whether other sources should be searched, and whether date limits are justified: those choices are part of the review method. Cochrane treats searching and study selection as core methods of a systematic review. PRISMA then specifies what information about that search should appear in the paper, including the full strategies.

My review method determines how I search. PRISMA tells me what information about that search should appear in the paper.

If the Methods section names PRISMA and never names the databases, the dates, or the strategy, the reporting guideline has been cited in place of the search method.

Does a PRISMA checklist replace a review protocol?

Before screening starts, a protocol may already have defined the question, eligibility criteria, search methods, outcomes, risk-of-bias assessment, and synthesis plan. That document is a plan for conduct, whereas PRISMA 2020 is written for reporting the completed review. There is a separate guideline, PRISMA-P, for systematic-review protocols, and the official PRISMA site describes PRISMA-P as guidance intended to support the development and reporting of those protocols. Completing the PRISMA 2020 checklist after finishing a review is a different task from having written a protocol in advance.

Do all reviews use the same PRISMA guideline?

The EQUATOR Network entry and the official PRISMA resources list a family of extensions around the main PRISMA 2020 checklist. Among others:

• PRISMA-P for systematic-review protocols;
• PRISMA-ScR for scoping reviews;
• PRISMA-S for reporting literature searches;
• extensions for diagnostic test accuracy reviews, network meta-analyses, harms, and individual participant data.

Name the specific guideline or extension you used. A scoping review reported “according to PRISMA” without “PRISMA-ScR” leaves the reader to guess which checklist was followed.

What should readers be able to reconstruct?

Print the Methods and Results and ask whether a stranger could recover the question, the eligibility rules, the databases and dates, the screening process, the data extracted, the bias assessment, the synthesis, and the limitations that affect the conclusions. A flow diagram plus a sentence that PRISMA was followed will not get them there. PRISMA helps make that information visible, and the review method determines how those steps were actually performed. If the Methods paragraph still says only that the review followed PRISMA, rewrite it so a stranger can tell which handbook, protocol, databases, and synthesis choices produced the results.

You do not conduct PRISMA. You conduct a systematic review. PRISMA helps you report that review clearly enough for someone else to judge the work.

References and useful policies

1. Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. PLoS Medicine. 2021;18(3):e1003583.
2. PRISMA. PRISMA 2020 statement.
3. Higgins JPT, Thomas J, Chandler J, et al., eds. Cochrane Handbook for Systematic Reviews of Interventions. Version 6.5. Cochrane; 2024.
4. EQUATOR Network. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews.
5. Moher D, Shamseer L, Clarke M, et al. Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement. Systematic Reviews. 2015;4(1):1.
6. PRISMA. PRISMA-Protocols.
7. Page MJ, Moher D, Bossuyt PM, et al. PRISMA 2020 explanation and elaboration: updated guidance and exemplars for reporting systematic reviews. BMJ. 2021;372:n160.
8. Shea BJ, Reeves BC, Wells G, et al. AMSTAR 2: a critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both. BMJ. 2017;358:j4008.
9. Tricco AC, Lillie E, Zarin W, et al. PRISMA extension for scoping reviews (PRISMA-ScR): checklist and explanation. Annals of Internal Medicine. 2018;169(7):467-473.
10. Rethlefsen ML, Kirtley S, Waffenschmidt S, et al. PRISMA-S: an extension to the PRISMA Statement for reporting literature searches in systematic reviews. Systematic Reviews. 2021;10(1):39.