PROSPERO (International Prospective Register of Systematic Reviews) is the public registry for systematic review protocols. You should register once your protocol is near-final, and crucially before you begin data extraction — PROSPERO rejects registrations if data extraction has already started (Eligibility). “Ready” means you can describe your question (PICO/PEO), eligibility criteria, search methods, selection and data-extraction process, risk-of-bias approach, and synthesis plan in clear, specific terms. Registering early creates a time-stamped record that reduces bias and prevents duplicate effort.

If you need a quick refresher on terms, see the glossary of SLR terminology. New to the workflow? Start with the quick-start guide. If you are still drafting your protocol, the SRT protocol development tool can help you structure the core sections you will enter into PROSPERO.

Why PROSPERO Registration Matters

Guarding Against Reporting Bias

One of PROSPERO's primary functions is to create a public, time-stamped record of your planned methods before you begin data extraction. This prospective registration helps prevent:

Selective outcome reporting - When researchers only report findings that support their hypotheses
Post-hoc outcome switching - Changing planned outcomes based on what the data shows
HARKing (Hypothesizing After Results are Known) - Presenting exploratory findings as if they were planned from the start

By registering your protocol early, you establish a clear record of your intended methods, making any deviations transparent and accountable.

Preventing Unnecessary Duplication

Research waste is a significant problem in academia. PROSPERO helps address this by:

Making ongoing work visible to other research teams
Allowing stakeholders to track relevant reviews in their field
Supporting efficient use of research funding by avoiding redundant efforts
Enabling collaboration between teams working on similar topics

Meeting Modern Research Standards

Registration is increasingly expected by:

Funding bodies who want to ensure research efficiency
Academic journals that require protocol registration for publication
Professional organizations promoting research transparency
Systematic review guidelines like PRISMA and Cochrane standards

What You Need Before Registration

PROSPERO requires a near-final protocol that demonstrates you've thought through your review methodology. Here's what you need to have ready:

Core Protocol Elements

Review Question and Background

Clear, focused question using PICO/PEO framework
Comprehensive background justifying the review's importance
Specific objectives and scope

Eligibility Criteria

Population: Who will be included (age, condition, setting)
Intervention/Exposure: What treatments or exposures you're studying
Comparator: What comparison groups you'll use
Outcomes: Primary and secondary measures
Study Designs: Types of research you'll include
Settings: Geographic or institutional boundaries

Search Strategy

Databases you'll search (PubMed, Cochrane, Web of Science, etc.)
Date limits and language restrictions
Grey literature sources
Supplementary search methods (reference checking, expert consultation)

Outcomes and Analysis Plan

Primary and secondary outcomes with clear definitions
Planned subgroup analyses or sensitivity analyses
Statistical methods for meta-analysis (if applicable)
Risk of bias assessment tools
Data synthesis approach (narrative, quantitative, or mixed methods)

PROSPERO's Core Dataset

PROSPERO requires completion of 22 mandatory fields covering:

Administrative details (title, dates, funding)
Review question and objectives
Methods (eligibility, search, selection, data extraction)
Analysis plan and risk assessment
Dissemination plans

An additional 18 optional fields allow you to provide more detail about complex reviews.

Step-by-Step Registration Process

Step 1: Prepare Your Account

Visit the PROSPERO website and create a free account. You'll need to provide basic contact information and institutional affiliation.

Step 2: Start Your Registration

Step 3: Complete Administrative Fields

Fill in essential details:

Review title (clear and descriptive)
Anticipated start/completion dates
Current review stage (must be pre-data extraction)
Funding sources and potential conflicts of interest
Team members and their roles

Step 4: Enter Methodological Details

This is where the detailed protocol information goes:

Review question in PICO/PEO format
Eligibility criteria with clear inclusion/exclusion rules
Search methods including full search strings
Data extraction plan - how you'll collect information from included studies
Risk of bias assessment - which tools you'll use
Synthesis methods - statistical approaches for meta-analysis

Aim for concise but comprehensive descriptions (typically 300-500 words per major section). Use structured formats with bullet points where appropriate.

Step 5: Submit and publish

Submit your completed form. PROSPERO carries out automatic checks as you enter data. A named guarantor must approve the record, and all named team members must confirm participation. Once those confirmations are completed, a registration number is assigned and the record is published immediately — there is no delay to publication (Register).

You can cite the assigned CRD number (for example, “CRD42023XXXXXX”) in your manuscript and protocol.

Managing Your Protocol After Registration

Handling Protocol Changes

Research protocols sometimes need adjustment based on real-world considerations. If you must deviate from your registered plan:

Document all changes with clear justifications
Update your PROSPERO record to maintain transparency
Report deviations in your final publication
Consider amendments for major changes (PROSPERO allows updates)

Linking to Final Publications

When you complete your review:

Cite your PROSPERO registration in the published manuscript
Include the CRD number in your PRISMA flow diagram
Reference the protocol in your methods section
Upload final results to PROSPERO if desired

Common Challenges and Solutions

Challenge: Getting Started

Solution: Use PROSPERO's online guidance and templates. Many institutions provide protocol development support. The SRT protocol development tool can also help you structure the fields PROSPERO requires.

Challenge: Keeping Within Word Limits

Solution: Focus on essential details. Use appendices for complex search strings or detailed analysis plans.

Challenge: Timing Your Registration

Solution: Register as early as possible but ensure your protocol is sufficiently developed. Remember: PROSPERO rejects records if data extraction has already started (Eligibility).

Challenge: Managing Team Contributions

Solution: Clearly define roles in the registration and ensure all team members review the final submission.

The Future of Protocol Registration

As research transparency becomes increasingly important, protocol registration is likely to become mandatory for more journals and funders. PROSPERO continues to evolve, with plans for enhanced search functionality, integration with other registries, and improved user experience.

By registering your systematic review protocol with PROSPERO, you're not just following best practices—you're contributing to a more transparent, efficient, and credible research ecosystem. The time investment in proper registration pays dividends throughout your review process and beyond.

Resources:

PROSPERO website: crd.york.ac.uk/prospero
PRISMA-P guidelines for protocol reporting
Cochrane Handbook: Chapter on protocol development

PROSPERO registration: how and when to register a systematic review