Systematic map -Frequently asked questions

Systematic maps are designed to map the breadth of evidence on a topic—often for policy questions—by cataloging studies across interventions, populations, outcomes, and study designs, then highlighting where evidence is abundant, thin, or missing. Like systematic reviews, they follow a rigorous, transparent process, but they prioritize coverage over synthesis. That makes them especially useful when a topic is broad or multifaceted—such as involving multiple interventions, multiple populations, multiple outcomes, or evidence that isn’t limited to primary studies.

The core purpose is practical: systematic maps help teams understand the state of knowledge, locate policy-relevant evidence, and surface knowledge gaps and “knowledge clusters” that may later be suitable for deeper secondary research. A common pathway is a two-stage approach: first use a systematic map to characterize the evidence base, then select smaller subsets of studies that can answer narrower questions through a full systematic review. In other words, systematic maps act as an evidence-scanning tool that can guide where more intensive synthesis is worth the effort.

A systematic map typically presents evidence in a structured matrix—intervention categories as rows and outcome domains as columns—so patterns become visible at a glance. The map can also include counts such as the number of articles, publications per year, studies by country, intervention types, and study designs. Trends over time, knowledge gaps, and knowledge clusters are identified by examining these distributions.

Many systematic maps use a “traffic light” quality scheme: red indicates low-quality evidence and green indicates high-quality evidence. Circle size often represents the volume of evidence, so areas with lots of studies stand out from those with sparse coverage. Filters—such as region, population subgroup, or study design—allow users to zoom in on specific slices of the evidence base. User-friendly features like summaries and links back to sources are also common, helping readers move from the map to the underlying studies.

Key distinctions separate systematic maps from systematic reviews. Systematic maps usually use broader, more descriptive map questions, while systematic reviews tend to focus on narrower questions that support qualitative, quantitative, or mixed-method synthesis. Search strategies in systematic maps can include both primary and secondary research without the same design restrictions that often apply in systematic reviews (for example, limiting to randomized controlled trials or to qualitative studies). Screening and data extraction in maps can rely on limited information rather than requiring full-text for every included record. Critical appraisal is optional in systematic maps, whereas it is compulsory in systematic reviews. Finally, systematic maps generally do not synthesize study results; they instead report trends, gaps, and clusters.

The transcript also distinguishes related approaches: evidence gap maps (developed by 3ie, the International Initiative for Impact Evaluation) are thematic collections of completed and ongoing systematic reviews and impact evaluations, built with similar mapping methods. Broader variants include “mega maps,” which cover large sectors and include only systematic reviews and other maps, and “maps of maps,” which aggregate maps across many sectors.

Methodologically, systematic maps follow six stages: forming the review team and stakeholders, searching for evidence, screening, coding, optional critical appraisal, and finally describing and visualizing the map. Protocols and frameworks (often using PEOS—population, exposure/intervention, outcomes, and study design—dimensions) guide how rows and columns are defined, how coding forms are built, and how results are analyzed and reported. Software tools mentioned include EP mapper (from EPPI-Centre/EP reviewer ecosystem), Tableau, and tools used by 3ie for evidence gap maps. The transcript closes with examples of published systematic maps and evidence gap maps in journals and on organizational websites, underscoring that these products can be disseminated as journal articles or guidance-linked reports.