PROSPERO is an international database of prospectively registered systematic reviews in health and social care. Key features from the review protocol are recorded and maintained as a permanent record. PROSPERO aims to provide a comprehensive listing of systematic reviews registered at inception to help avoid unplanned duplication and enable comparison of reported review methods with what was planned in the protocol.
The development and ongoing management of PROSPERO is supported by CRD’s core work programme which is funded by the National Institute for Health Research, England; the Department of Health, Public Health Agency, Northern Ireland and the National Institute for Social Care and Health Research, Welsh Government
The development and implementation of PROSPERO has been led by Alison Booth and Lesley Stewart at CRD guided by members of the Advisory Group:
Research Fellow, CRD, University of York, York, UK.
Centre for Public Health, Queen's University Belfast, Belfast, UK, (Chair).
Metaxis, Oxford, UK.
Research Translation Branch, National Health & Medical Research Council, Canberra, Australia.
Division of Clinical Neurosciences, College of Medicine and Veterinary Medicine, University of Edinburgh; Florey Neurosciences Unit, Melbourne, Australia; Collaborative Approach to Meta-Analysis and Review of Animal Data in Experimental Studies (CAMARADES).
Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada; Department of Epidemiology and Community Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Canada.
Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London, UK.
Director of CRD, University of York, York, UK.
The PROSPERO Advisory Group Statement of Founding Principles centres on free access both to register and search the database and being as inclusive as possible while achieving the key aims of avoiding duplication and minimising bias in systematic reviews.
Why is prospective registration of systematic reviews important?
Registration provides transparency in the review process. It helps counter publication bias by providing a permanent record of prospectively registered reviews, irrespective of whether they are eventually published or not. It helps safeguard against reporting biases by revealing any differences between the methods or outcomes reported in the published review and those planned in the registered protocol. This should improve quality and increase confidence that policy or practice informed by the findings of a systematic review is drawing on best-quality evidence. Registration allows those commissioning or planning reviews to identify whether there are any reviews already underway that address their topic of interest. This helps avoid unintended and economically wasteful duplication of effort.
What is registration?
Registration in PROSPERO involves the submission and publication of key information about the design and conduct of a systematic review. Applications are assessed to ensure that they fall within scope and that the required data have been provided. No quality assessment or peer review is involved. Registration records are published on an open access electronic database.
Registration information can be amended should plans change. All such changes are published and an audit trail of previous versions made available in the public record.
Registration records are permanent and registrants are asked to provide links to subsequent reports and publications. The record can be ‘re-activated’ when a completed review is updated.
PROSPERO assigns each registered review with a unique registration number. This number can be cited in publications and reports to provide the link between the planned and completed review, as recommended by PRISMA 2009 and many publishers.
Who will benefit from registration?
PROSPERO will assist:
- Researchers by allowing them to comply with PRISMA, providing a public record of their planned methods and raising awareness of their review. Use of the unique registration number will also allow them to track subsequent use of their review and monitor impact.
- Commissioners and funders by allowing them to identify ongoing and unpublished reviews addressing their topic of interest, thereby helping avoid unplanned duplication.
- Peer reviewers by allowing comparison of manuscript findings with the review protocol.
- Journal Editors by providing a safeguard against reporting biases and providing access to key protocol features that they can utilise in the peer review process, where appropriate.
- Guideline developers by providing information about forthcoming reviews which may assist in planning and timing of guideline development.
- The public by providing free and open access to information about ongoing systematic reviews, by encouraging transparency in the systematic review process, by helping ensure that health and social care decisions that may affect them are known to be based on good quality systematic review evidence, and by helping to avoid wasting money on unintended duplication of effort.
PROSPERO will create opportunities for methodological research.
The registration data set
The aim of registration is to capture those attributes of a review that are likely to be important in the avoidance of bias, and to provide enough information to help people planning reviews in a similar area to decide whether or not to proceed. The registration data set does not seek to capture all the information that should be included in a systematic review protocol.
The registration form is divided into four sections and contains 22 required fields and 18 optional fields agreed through international consultation. ‘Required’ fields must be completed before a registration can be submitted; these are indicated with an asterisk in the list below.
Dataset with brief guidance notes in pdf format.
Review title and timescale
- Review title*
- Original language title
- Anticipated or actual start date*
- Anticipated completion date*
- Stage of review at time of registration*
Review team details
- Named contact*
- Named contact email*
- Named contact address
- Named contact phone number
- Review team members and their organisational affiliations
- Organisational affiliation of the review*
- Funding sources/ sponsors*
- Conflicts of interest*
- Review question(s)*
- URL to search strategy
- Condition or domain being studied*
- Participants/ population*
- Intervention(s), exposure(s)*
- Comparator(s)/ control*
- Types of study to be included initially*
- Primary outcome(s)*
- Secondary outcomes*
- Data extraction (selection and coding)
- Risk of bias (quality) assessment*
- Strategy for data synthesis*
- Analysis of subgroups or subsets*
- Type of review
- Other registration details
- Reference and/or URL for published protocol
- Dissemination plans
- Details of any existing review of the same topic by the same authors
- Review status*
- Any other information
- Link to publication of final report
Cochrane protocols on PROSPERO
Key details from new Cochrane protocols are automatically uploaded into PROSPERO. These records are clearly marked with [Cochrane protocol] at the end of the title. Affiliation to the Cochrane Library and links to the full protocol on the Cochrane Library are automatically added to the PROSPERO record. The mechanism for uploading was first piloted with protocols added to the Cochrane Library in October 2013. This is therefore the earliest data for inclusion of new Cochrane protocols in PROSPERO.
In order to avoid adding to the workload of Cochrane reviewers and/or editors, the loading of new Cochrane protocols is fully automated. Most of the PROSPERO record is populated with data taken directly from the corresponding fields in the Cochrane Library record. No changes are made to the data, however the following administrative actions and defaults should be noted:
Intervention(s), exposures and Comparator(s)/control
Information about the intervention and the comparator/control is given in a single field in the Cochrane record. To accommodate the separate fields in PROSPERO, our administration staff move the details of the Comparator/control to the relevant field. Where the wording is such that they cannot be separated the information is left in the Intervention(s), exposures field and a note to ‘See above’ is entered in the Comparator(s)/control field in PROSPERO. [N.B. This is only acceptable for the automatic loading of Cochrane protocols and is not accepted in non-Cochrane submissions for registration.]
The lead authors of new Cochrane protocols added to PROSPERO are sent an email to notify them of the creation of the record on PROSPERO. They are also notified when the record is automatically updated to reflect publication of the review in the Cochrane Library. In the rare event of a major amendment to a Cochrane protocol, the PROSPERO administration team will email the lead author for the Cochrane review and ask them for the stage of the review at the time of the amendment.
Anticipated or actual start date
The date given here is the date the record was loaded into PROSPERO.
Anticipated completion date
This date is derived from the Cochrane Library record when available. In the absence of this information the date of entry into PROSPERO plus two years is entered.
Stage of review at the time of this submission
This information is not available from the Cochrane library record. We have therefore agreed to set all Cochrane protocols to the same stage of review when they are loaded. This is that Preliminary searches have been completed and piloting of the study selection process started. This default setting was agree given that only new Cochrane protocols are being added and in accordance with Cochrane process protocols are finalised before work progresses on the review.
Integrity of data and prospective registration
PROSPERO relies on the integrity of researchers for the accuracy of the data supplied, and the named contacts are accountable for the content of their records. We routinely monitor the time frame given in submissions and seek clarification where this appears overly ambitious prior to confirming registration and providing a PROSPERO registration number. Amendments and updates to the record are made transparent in the audit trail within each record.
On rare occasions, peer reviewers and editors using PROSPERO to compare what was planned with what is reported in the final manuscript, have identified that the initial registration date in PROSPERO post-dates the manuscript submission date to the journal. In these cases the logical explanation is that the stage of review was inaccurately completed in the PROSPERO registration form; otherwise the submission would have been rejected. In such cases, the named contact will be alerted to the issue and given the opportunity to respond within two weeks. If it is confirmed that incorrect information was provided, or no response is received, the content of the PROSPERO record will be removed, leaving the title and the details of the named contact and the following statement:
Since publication of this record it has been established that information provided initially about the stage of the review and anticipated completion date was inaccurate. The review had actually progressed beyond the stage of eligibility for PROSPERO.
Prospective registration aims to facilitate the comparison of reported review findings with what was planned a priori in the protocol. Reviews should ideally be registered before screening against eligibility criteria commences. However, reviews are currently accepted provided they have not progressed beyond the completion of data extraction.
Protocol details for this review should be sought from the named contact.
How to cite a PROSPERO record
Author(s). Title. PROSPERO: International prospective register of systematic reviews. Year of registration. Unique Identification number. Available from: hyperlink for the record.
Example: Phillips R, Wade R, Myers L, Hardman M, Sutton A, Stewart L. A systematic review of prognostic serum markers in febrile neutropenic episodes in children and young people undergoing treatment for malignant disease. PROSPERO: International prospective register of systematic reviews. 2011: CRD42011100485. Available from: http://www.crd.york.ac.uk/prospero/display_record.asp?ID=CRD42011001684
Suggested wording for inclusion in a final report
1. Where the protocol has been published in full elsewhere:
The protocol for this systematic review was registered on PROSPERO (Unique ID number) and is available in full on the Name of organisation website (URL).
Example: The protocol for this systematic review was registered on PROSPERO (CRD42011001438) and is available in full on the NIHR HTA programme website (www.hta.ac.uk/2283).
2. Where the protocol has not been published and is not available anywhere other than PROSPERO:
Details of the protocol for this systematic review were registered on PROSPERO and can be accessed at www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42011001752
Encouraging registration in PROSPERO
We encourage commissioners and journal editors to promote registration of systematic reviews in PROSPERO.
The UK NIHR has made protocol registration a condition of funding for all the eligible systematic reviews they commission. The model NIHR have adopted requires little additional effort on their part. The funder notifies the researchers of the requirement to register. The researchers then register their review and send the funder the unique registration number issued by PROSPERO. On receipt of this number, the funder continues with contractual/funding arrangements as usual. Further information is available in Example of registration requirements. Following implementation, the numbers registering in the UK have risen considerably and the registration process and turn round time for publication appear to have been acceptable to researchers.
At the publication end of the review process, PLoS journals, BMJ and BMJ Open, BioMed Central and BJOG all recommend in their instructions to authors that details of protocol registration be included in manuscripts of both systematic review protocols and their final review reports/articles.
Promotion of PROSPERO
General awareness raising activities are undertaken on an ongoing basis. These include conference presentations, workshops and stands and publication of papers. We also provide information to others willing to raise awareness about PROSPERO such as those running systematic review training courses. We would be pleased to supply A5 postcards explaining How to register a review on PROSPERO and some generic PowerPoint slides are provided below. For additional information, slides or copies of the postcard please contact Alison Booth at email@example.com.
Development and progress of PROSPERO (Powerpoint slides)
Registering a systematic review on PROSPERO (Powerpoint slides)
Reducing unplanned duplication of systematic reviews
PROSPERO’s single searchable listing of on-going systematic reviews enables commissioners and researchers to check whether there is an existing review that addresses their topic of interest, before planning a new review. The aim is to reduce unplanned duplication of reviews and promote efficient use of resources. The NIHR HTA Programme demonstrated success for this aim when they decided not to commission research on restricted elimination diet in Attention Deficit-Hyperactivity Disorder when PROSPERO revealed that an overlapping research project was already in progress.
However, there are appropriate and valuable reasons for undertaking independent replication of reviews, diverse ways of answering specific questions, and advances in knowledge can stem from looking at things from a different angle. We do not feel it would be appropriate, or indeed possible, for us to regulate submissions with similar titles and therefore do no attempt to do so.
PROSPERO relies on the integrity of researchers for the accuracy of the data supplied and by providing access to details of ongoing reviews, facilitates appropriate planning and justification of reviews. Each published record contains the anticipated start date, the anticipated completion date and the date on which the record was accepted for publication on PROSPERO. This enables users to assess for themselves the chronology of records entered on the database.
Are there risks from registration?
Some researchers have expressed concern that titles and protocol details registered in PROSPERO could be copied and used by other researchers. Conversely others have raised concerns about reviews being registered but never completed, discouraging others from addressing the same topic. PROSPERO does not preclude registration of duplicate reviews as this would be counter to the open and collaborative aims of registration. We take a pragmatic approach and trust to the integrity of researchers.
All records are permanent and contain the date of initial registration on PROSPERO, the anticipated start date and the anticipated completion date. It is inevitable that some reviews will take longer than expected, and a facility to amend these dates is provided. Every change is documented in the public archive such that users can consider whether the delays appear appropriate and justified. All records also contain the name and email address of the named contact for the review, who can be approached for information about progress. Users can therefore make their own judgements about the likelihood of completion of registered reviews, degree of overlap with their own review topic and whether duplication might be beneficial. Highlighting areas of overlapping interest might even generate collaborative approaches.
Commissioners and funders or membership organisations may use information from PROSPERO to help decide what research is undertaken by whom within their funding stream or organisation. PROSPERO does not have, or seek to have, any mandate to regulate the systematic review process.
Methodological research using PROSPERO data
CRD and the PROSPERO advisory group have a programme of methodological research work planned.
The information being collected and published in PROSPERO will be of interest to many. As a matter of courtesy and in order to avoid duplication of effort, we ask that anyone planning research using PROSPERO data provide us with brief details of their work so we can record it here. Publications or presentations that use information obtained from PROSPERO should cite and acknowledge PROSPERO as the source of data. We would appreciate receiving details of such publications so that we can link to them from these pages.