What Is a Systematic Review Protocol?

A systematic review protocol is a written plan, prepared before the review begins, that sets out the question, eligibility criteria, search methods, selection, data collection, bias assessment and analysis. It guards against changing methods in response to results and lets readers see whether the review followed its plan.

Why write one

• Reduces bias from post hoc decisions.
• Helps the team agree methods and tasks.
• Allows peers to comment.
• Supports registration and publication.
• Helps editors and readers detect selective reporting.

Essential contents

1. Title and review type; team and contributions; funding and conflicts.
2. Rationale and objectives.
3. Eligibility criteria (PICOS) and outcomes, primary and secondary.
4. Information sources and draft search strategy.
5. Selection process.
6. Data items and extraction process.
7. Risk-of-bias assessment method.
8. Planned synthesis: when to pool, effect measures, heterogeneity, subgroup and sensitivity analyses, small-study effects.
9. Certainty assessment.
10. Timeline and plans for amendments.

Amendments

If you must change the protocol, record what changed, when and why, and report the change in the final review.

Illustrative example

Invented for teaching. The protocol states that the primary outcome is 12-month fracture incidence and that trials with fewer than 20 participants will be excluded. When screening reveals many small trials, the team keeps the rule instead of changing it to include more studies, and notes a planned sensitivity analysis.

Practical tips

Write the protocol collaboratively and ask someone outside the team to read it. Use a reporting template such as the PRISMA-P items as a prompt for contents (check the official source for the current version). Save dated versions, and plan how outcomes will be handled if some studies report them differently, because this is where protocol deviations often arise.

Common pitfalls

• Writing the protocol after seeing the results.
• Failing to document amendments.

Key takeaways

• A protocol is a plan, a promise and a record.
• Register and, where possible, publish it.

This page is general educational information about research methods. It is not medical, legal or regulatory advice; follow your institution's ethics board and your target journal's instructions.