Systematic review protocol & PROSPERO registration
The protocol is the single most important document in a systematic review — and the one most students skip. It’s the full plan, written and registered before you screen a single study. Fixing your method in advance is what stops the review from being quietly shaped by the results, and a public, time-stamped registration is what lets a reviewer trust that you didn’t move the goalposts.
What a protocol contains
A protocol pins down every decision before you meet the evidence:
- Background & objective — the rationale and the focused question.
- Eligibility criteria — your inclusion/exclusion rules, framed with PICO.
- Search strategy — databases, the full search string, date limits, grey literature (see building a search strategy).
- Screening & selection — two independent reviewers, how disagreements are resolved.
- Data extraction — what variables you’ll pull and on what form.
- Risk of bias — which appraisal tool you’ll use.
- Synthesis plan — meta-analysis or narrative synthesis, and the rules for choosing.
The reporting standard for a protocol is PRISMA-P — the protocol companion to the PRISMA 2020 statement that governs the finished review.
Registering on PROSPERO
PROSPERO is the international prospective register of systematic reviews. Registering there before you begin time-stamps your plan, makes your intentions public, and helps prevent duplicate reviews and selective reporting. Many journals now ask for a registration number at submission. The mechanism is the value: because your plan is public and dated, anyone can check whether what you did matches what you said — and any deviation has to be declared and justified, not hidden.
Why this protects the review
Without a registered protocol it’s easy — often unconsciously — to drop an inconvenient outcome, loosen an eligibility rule to include a striking study, or switch the analysis after seeing the data. Pre-registration closes those doors. It’s the same logic as a trial protocol: decide the method while you’re still honest about not knowing the answer.
Get the free Systematic Review toolkit
A PRISMA-P–aligned protocol template, a PICO worksheet, and a search-log template from The Dissertation Literature Review Sprint. We’ll email you the download link.
Frequently asked questions
What is a protocol?
The full plan for the review — question, eligibility, search, screening, extraction, risk of bias, synthesis — finalised before you start screening.
What is PROSPERO?
The international prospective register of systematic reviews; register your protocol there before you begin.
Why register before starting?
To prevent outcome switching and post-hoc changes that bias conclusions — the public, time-stamped plan keeps you honest.
What is PRISMA-P?
The PRISMA extension for protocols — the checklist for what a protocol should report.