PROSPERO Registration

PROSPERO registration is the act of submitting a systematic review’s protocol — its research question, PICO framework, search strategy, eligibility criteria, and planned analysis methods — to the International Prospective Register of Systematic Reviews (PROSPERO) before the review team has progressed beyond data extraction. PROSPERO is maintained by the Centre for Reviews and Dissemination (CRD) at the University of York and has been funded by the UK’s National Institute for Health and Care Research (NIHR) since its 2011 launch, making it the world’s first prospective register of systematic reviews. A successful submission is checked and published as a permanent, publicly citable, time-stamped record identified by a unique number with a “CRD42” prefix.

Why register a protocol before conducting the review

Registering on PROSPERO serves the same underlying purpose as prospective clinical trial registration on registries such as ClinicalTrials.gov, applied to evidence synthesis rather than primary research:

• Reduces unplanned duplication. A public, searchable record lets other teams see that a review on a given question is already underway before they commit resources to the same synthesis.
• Creates an audit trail against the pre-specified plan. Because the protocol is time-stamped before results are known, anyone can later compare the completed review against what the authors originally said they would do — including the primary outcome, comparators, and planned subgroup or sensitivity analyses.
• Reduces outcome-reporting and selective-reporting bias. Registration makes it harder to quietly drop an unfavourable outcome, add a favourable one after the fact, or narrow the review question once early results are visible. Any change from the registered plan should be declared and dated, not silently absorbed into the final manuscript.

This is the same rationale behind pre-registration of primary studies and registered-report Stage-1 protocols more broadly — PROSPERO is simply the discipline-specific implementation for systematic reviews with a health-related outcome.

Scope: what PROSPERO covers, and what it doesn’t

PROSPERO is not a general-purpose register for every kind of literature review. Eligibility is restricted to systematic reviews — of interventions, diagnosis, prognosis, aetiology, risk factors, genetic associations, or epidemiology — that have a health-related outcome, defined broadly. Since 2021 that scope extends beyond clinical medicine into social care, welfare, public health, education, crime and justice, and international development, but only where a health-related outcome is present; a review without one is out of scope regardless of subject matter.

Explicitly excluded: scoping reviews and narrative literature reviews are not eligible for PROSPERO, whatever their topic, because they do not follow the pre-specified, outcome-driven design the register exists to track (see literature review vs. systematic review vs. scoping review for how these designs differ). Registration is also time-limited within a review’s lifecycle: CRD accepts submissions up to the point data extraction has been completed, but not after — a review submitted once extraction is already finished is retrospective in substance even if labelled prospective, and undermines the audit-trail purpose above.

The registration process

In outline, registering a protocol on PROSPERO involves:

1. Draft a full protocol first. PROSPERO expects a complete protocol, not a placeholder outline — most reviewers structure this using the PRISMA-P 2015 checklist for systematic review and meta-analysis protocols (see protocol paper) so the submission covers PICO, search strategy, eligibility criteria, data extraction and synthesis plans, and risk-of-bias assessment methods in one pass.
2. Submit before formal screening is complete. Ideally this happens before title/abstract screening begins; registration remains accepted as long as full-text screening and data extraction have not yet been completed. If a review’s stage of progress is unclear, CRD recommends contacting the register directly for advice before submitting.
3. Registration is free. There is no charge to register, in keeping with PROSPERO’s public-good, NIHR-funded status.
4. Records are checked before publication. Following a March 2025 platform redesign, submissions go through automated and editorial checks and are published once all listed record authors have approved the content, generally within a short turnaround.
5. Keep the record current. Registrants are responsible for the accuracy of what they submit and for updating the record (e.g., amendments to the search strategy or outcomes, with dates) as the review progresses.
6. Cite the registration number. The resulting CRD42-prefixed identifier belongs in the review’s eventual publication — typically in the abstract and methods, alongside PRISMA 2020 reporting — so editors, peer reviewers, and readers can verify the review was planned before its results were known.

For the general mechanics of writing and registering a study protocol outside the PROSPERO-specific context (including non-health-outcome and non-systematic-review designs), see Preregistration of a Study Protocol. For the reporting standard that governs the completed review itself, see PRISMA and Systematic Review Methodology.

References

• Booth A, Clarke M, Dooley G, Ghersi D, Moher D, Petticrew M, Stewart L. “The nuts and bolts of PROSPERO: an international prospective register of systematic reviews.” Systematic Reviews. 2012;1:2.
• Page MJ, Shamseer L, Tricco AC. “Registration of systematic reviews in PROSPERO: 30,000 records and counting.” Systematic Reviews. 2018;7:32.
• Shamseer L, Moher D, Clarke M, et al. “Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) 2015: elaboration and explanation.” BMJ. 2015;349:g7647.
• Centre for Reviews and Dissemination, University of York — PROSPERO register: crd.york.ac.uk/prospero.