Will a journal reject a review because registration was retrospective?

Most will not, provided it is disclosed. Some journals require prospective registration for certain review types, and a minority of clinical journals apply it strictly, so check the instructions to authors before submission rather than after. Undisclosed retrospective registration is a much more serious problem than disclosed retrospective registration.

PROSPERO turned down our record. What now?

PROSPERO restricts registration to reviews with a health-related outcome and generally will not accept records where data extraction has begun. If it declines, INPLASY and the Open Science Framework are alternatives, and a preprinted protocol is a reasonable fallback. Whichever route you take, describe the timing accurately.

Can we register a scoping review?

PROSPERO does not accept scoping reviews. The usual routes are the Open Science Framework, Figshare, or publication of the protocol in a journal that accepts them. PRISMA-ScR does not require registration, but it does expect you to state whether a protocol exists and where it can be accessed.

Retrospective Registration: What to Do When the Search Has Already Run

Registering after the search has started isn't fatal, but it changes what registration proves. How to register honestly and what reviewers check.

14 September 20265 min

A common situation: the team has been working for two months, the search is done, screening is half finished, and someone asks whether the review was registered. It was not.

This happens often enough that it is worth treating as a normal problem with a correct answer rather than a disaster. The correct answer is to register now, disclose the timing accurately, and understand what the registration can and cannot demonstrate.

What registration actually proves

A prospective registration is a timestamped record that certain decisions were made before the evidence was seen. That is its entire function. It does not certify quality, it is not peer reviewed, and it confers no priority over anyone else working on the same question.

Its value comes from the sequence. When a registered protocol specifies the primary outcome and the analysis model before any effect estimate exists, a reader can rule out one specific failure mode: that the analysis was shaped by the results.

Register after the search and you keep some of that value and lose some. Eligibility criteria and outcomes recorded before screening is complete still constrain the decisions that follow. What you can no longer claim is that they were fixed before the literature was visible.

Register anyway, and be exact about timing

PROSPERO accepts records for reviews where data extraction has not yet started and asks for the anticipated or actual start date. INPLASY records the submission date on the public record. Both give a date that a reader can compare against your reported search date, which means the timing will be visible whether or not you draw attention to it.

Since it is visible, draw attention to it. A methods sentence along these lines does the job:

"The review was registered with PROSPERO on 12 May 2026 (CRD42026XXXXXX). Registration followed completion of the electronic searches on 28 April 2026 but preceded full-text screening and any data extraction. Eligibility criteria and the analysis plan were finalised before any effect estimates were seen."

That sentence is honest, it is specific, and it forecloses the reviewer's question. Silence invites the reviewer to work out the sequence themselves and to assume the least generous version.

What you cannot do

Do not backdate. Do not describe a retrospective registration as prospective. Do not write the registered outcomes to match what you have already found reported in the studies, then present them as prespecified.

This last one is the tempting error, because it feels like tidying. It is the precise thing registration exists to prevent, and it converts an ordinary procedural lapse into a misrepresentation.

If extraction is already complete

If effect estimates have been extracted and seen, registration adds much less, and some registries will decline the record. You still have options.

Publish a protocol as a standalone paper or preprint, describing accurately what was done and when. Several journals publish systematic review protocols, and Systematic Reviews accepts them. State plainly in the review that registration was not prospective and explain the sequence of decisions.

Alternatively, run the analysis you would have prespecified and report it as the primary result, with any post hoc variants labelled as such. What reviewers are trying to assess is whether the reported analysis was selected from among several the team had seen. Showing them the full set is a partial substitute for having committed in advance.

What a reviewer checks

Three things, in this order. Whether a registration number is given at all. Whether the registration date precedes the reported search date. And whether the outcomes and analyses in the registry match those in the manuscript.

The third check catches more manuscripts than the first two, and it catches them in reviews that were prospectively registered. A registration nobody consults after submission is a wasted asset. Read your own record before you write the methods section.

References

Booth, A., Clarke, M., Dooley, G., Ghersi, D., Moher, D., Petticrew, M., & Stewart, L. (2012). The nuts and bolts of PROSPERO: An international prospective register of systematic reviews. Systematic Reviews, 1, 2. https://doi.org/10.1186/2046-4053-1-2

Page, M. J., McKenzie, J. E., Bossuyt, P. M., Boutron, I., Hoffmann, T. C., Mulrow, C. D., Shamseer, L., Tetzlaff, J. M., Akl, E. A., Brennan, S. E., Chou, R., Glanville, J., Grimshaw, J. M., Hróbjartsson, A., Lalu, M. M., Li, T., Loder, E. W., Mayo-Wilson, E., McDonald, S., … Moher, D. (2021). The PRISMA 2020 statement: An updated guideline for reporting systematic reviews. BMJ, 372, n71. https://doi.org/10.1136/bmj.n71

Shamseer, L., Moher, D., Clarke, M., Ghersi, D., Liberati, A., Petticrew, M., Shekelle, P., & Stewart, L. A. (2015). Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015: Elaboration and explanation. BMJ, 350, g7647. https://doi.org/10.1136/bmj.g7647

Tricco, A. C., Lillie, E., Zarin, W., O'Brien, K. K., Colquhoun, H., Levac, D., Moher, D., Peters, M. D. J., Horsley, T., Weeks, L., Hempel, S., Akl, E. A., Chang, C., McGowan, J., Stewart, L., Hartling, L., Aldcroft, A., Wilson, M. G., Garritty, C., … Straus, S. E. (2018). PRISMA extension for scoping reviews (PRISMA-ScR): Checklist and explanation. Annals of Internal Medicine, 169(7), 467–473. https://doi.org/10.7326/M18-0850

Common questions

Will a journal reject a review because registration was retrospective?: Most will not, provided it is disclosed. Some journals require prospective registration for certain review types, and a minority of clinical journals apply it strictly, so check the instructions to authors before submission rather than after. Undisclosed retrospective registration is a much more serious problem than disclosed retrospective registration.
PROSPERO turned down our record. What now?: PROSPERO restricts registration to reviews with a health-related outcome and generally will not accept records where data extraction has begun. If it declines, INPLASY and the Open Science Framework are alternatives, and a preprinted protocol is a reasonable fallback. Whichever route you take, describe the timing accurately.
Can we register a scoping review?: PROSPERO does not accept scoping reviews. The usual routes are the Open Science Framework, Figshare, or publication of the protocol in a journal that accepts them. PRISMA-ScR does not require registration, but it does expect you to state whether a protocol exists and where it can be accessed.