Protocol-based Meta-analysis — Pre-registered Quantitative Evidence Synthesis

A protocol-based meta-analysis is a meta-analysis conducted according to a detailed, pre-registered protocol that specifies all key methodological decisions — research questions, eligibility criteria, search strategy, outcome measures, and statistical methods — before data collection begins. Pre-registration, typically through PROSPERO or a comparable registry, distinguishes this approach from post-hoc or exploratory meta-analyses and substantially reduces the risk of selective reporting and outcome switching.