SYSTEMATIC REVIEW article
Front. Res. Metr. Anal.
Sec. Research Methods
What Evidence Syntheses Reveal About PROSPERO, INPLASY, OSF, the Research Registry, and protocols.io: A Meta-Research Study
Raissa Tabosa Ferreira 1
Manuela Queiroz Reis 1
Maria Heloísa Pignataro Lange 1
Maycon Willian Fontes da Costa 1
Giovanna Kettlen Mendes Silva 1
Anne Beatriz Oliveira Lemos 1
Douglas Raphael Lela Dias 1
Maria de Lourdes Santos Viana 1
Ana Luiza Oliveira dos Santos 1
Ana Beatriz Maia Fernandes 1
Manuella Rocha Boaventura Pinheiro 1
Clarice Wanderley de Sousa 1
Kevin Henrique Azevedo Duarte 1
Gustavo Fernandes 2
Carlos Marcelo da Silva Figueredo 3
Mario Viana Vettore 4
Marcelo Marotta Araujo 5
Fabio Gamboa Ritto 6
João Vitor dos Santos Canellas 7,1
1. Department of Dentistry, School of Health Sciences, University of Brasilia - UnB, Brasília-DF, Brazil
2. A T Still University Missouri School of Dentistry & Oral Health, Kirksville, United States
3. Griffith University School of Medicine and Dentistry, Gold Coast, Australia
4. Aarhus Universitet Institut for Odontologi og Oral Sundhed, Aarhus, Denmark
5. Department of Restorative Dentistry, Institute of Science and Technology, São Paulo State University (UNESP), São José dos Campos-SP, Brazil
6. Department of Oral and Maxillofacial Surgery, College of Dentistry, University of Oklahoma, Oklahoma, United States
7. INPLASY, Inc., Middletown, United States
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Abstract
Background: This meta-research investigated how information about protocol registration has been reported in evidence syntheses published from 2020 to 2025 and registered in PROSPERO, INPLASY, OSF, the Research Registry, or protocols.io. Methods: We analyzed 4,750 studies covering various evidence synthesis types. Data were collected on registry use, reporting transparency, and accessibility features. Statistical comparisons included effect sizes and 95% confidence intervals. Results: PROSPERO remained the most widely used, with registrations from 70 countries. Among studies registered in non-PROSPERO platforms, over 90% were found in INPLASY and OSF. Compared with PROSPERO, both registries showed stronger reporting practices, with higher protocol status updates in INPLASY and more hyperlinks in OSF. However, a hyperlink did not always ensure public availability, as many OSF protocols required author authorization. Protocols in PROSPERO were associated with multiple publishers. In contrast, INPLASY protocols were more frequently linked to open-access journals, particularly those published by Frontiers and MDPI. Conclusion: Although PROSPERO remains the reference registry, INPLASY and OSF are playing an increasingly important role in promoting openness and accessibility. Researchers are encouraged to search multiple registries, especially PROSPERO, INPLASY, and OSF, before starting a new study to minimize duplication of efforts.
Summary
Keywords
Evidence synthesis, INPLASY, Open Science Framework, Prospero, protocol, Registration, Scoping review, Systematic review
Received
03 November 2025
Accepted
29 January 2026
Copyright
© 2026 Ferreira, Reis, Lange, da Costa, Silva, Lemos, Dias, Viana, dos Santos, Fernandes, Pinheiro, de Sousa, Duarte, Fernandes, Figueredo, Vettore, Araujo, Ritto and Canellas. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: João Vitor dos Santos Canellas
Disclaimer
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