A systematic review protocol is a detailed plan written before you begin searching databases to ensure your review remains objective, transparent, and methodologically sound.
Why Write a Protocol First?
Creating your protocol upfront prevents bias from creeping in after you've seen preliminary results. It forces you to define your research question, inclusion criteria, search strategy, and analysis methods before any data collection begins. Many journals and funding bodies now require protocol registration (often through PROSPERO) to ensure reviewers aren't cherry-picking studies or changing methods mid-stream.
Essential Protocol Components
Research Question and Objectives: Frame your question using PICO (Population, Intervention, Comparison, Outcome) or a similar framework. Be specific about what you're investigating and why it matters.
Eligibility Criteria: Define exactly which studies you'll include and exclude. Specify study designs (RCTs, cohort studies, etc.), publication dates, languages, and any other boundaries. This prevents subjective decisions later when you're screening hundreds of papers.
Search Strategy: Document which databases you'll search (PubMed, Web of Science, Scopus, etc.), your Boolean search strings, and any filters you'll apply. List the specific keywords and MeSH terms you'll use. When planning complex searches that need to exclude certain subtopics while including others, tools like WisPaper's Scholar Search can help refine your query logic before you commit it to your protocol.
Screening Process: Outline how many reviewers will screen titles/abstracts, how you'll resolve disagreements, and what software you'll use for duplicate removal.
Data Extraction Plan: Create a template showing exactly what information you'll extract from each included study—outcomes, sample sizes, methodological details, etc.
Quality Assessment: Specify which risk-of-bias tools you'll use (Cochrane RoB 2, Newcastle-Ottawa Scale, etc.).
Synthesis Methods: State whether you'll conduct meta-analysis or narrative synthesis and under what conditions.
Registration and Revision
Register your protocol in PROSPERO or publish it in a protocol journal before starting your searches. If you must revise the protocol later, document all changes with justifications—transparency is key to maintaining credibility.
