Evidence Synthesis: Finding, appraising and synthesizing research

Steps in Evidence Synthesis

1. Identify your research question.  Formulate a clear, well-defined research question of appropriate scope. Define your terminology. Find existing reviews on your topic to inform the development of your research question, identify gaps, and confirm that you are not duplicating the efforts of previous reviews. Consider using a framework like PICO (see below) to define your question scope.
2. Define inclusion and exclusion criteria. Clearly state the criteria you will use to determine whether or not a study will be included in your search.  Consider study populations, study design, intervention types, comparison groups, measured outcomes.
3. Search for studies. Run your searches in the databases that you've identified as relevant to your topic. Work with a librarian to help you design comprehensive search strategies across a variety of databases. Approach the gray literature methodically and purposefully. Collect ALL of the retrieved records from each search into a reference manager, such as Zotero, and de-duplicate the library prior to screening.
4. Select studies for inclusion based on pre-defined criteria. Start with a title/abstract screening to remove studies that are clearly not related to your topic. Use your inclusion/exclusion criteria to screen the full-text of studies. It is highly recommended that two independent reviewer screen all studies, resolving areas of disagreement by consensus.
5. Extract data from included studies. Use a spreadsheet, or systematic review software, to extract all relevant data from each included study. It is recommended that you pilot your data extraction tool, to determine if other fields should be included or existing fields clarified.
6. (For systematic reviews) Evaluate the risk of bias of included studies. Use a quality assessment or risk of bias tool (such as those found in the LATITUDES Network site) to assess the potential biases of studies in regards to study design and other factors. You can adapt existing tools to best meet the needs of your review, depending on the types of studies included.
7. Present results and assess the quality of evidence. Clearly present your findings, including detailed methodology (such as search strategies used, selection criteria, etc.) such that your review can be easily updated in the future with new research findings. Perform a meta-analysis if the studies allow. Provide recommendations for practice and policy-making if sufficient, high quality evidence exists, or future directions for research to fill existing gaps in knowledge or to strengthen the body of evidence.

You may choose to register a protocol prior to conducting your review. This will improve transparency and reproducibility, but will also ensure that other research teams do not duplicate efforts. If you are working with the Cochrane or Campbell Collaborations, you will publish your protocol with those organizations. If you are working independently, consider registration with:

Open Science Framework:  An open source web application that connects and supports the research workflow. Researchers use the OSF to collaborate, document, archive, share, and register research projects, materials, and data. OSF can be used to pre-register a review protocol and to share documents such as a Zotero library, search strategies, and data extraction forms. 

PROSPERO: An international database of prospectively registered systematic reviews in health and social care. Key features from the review protocol are recorded and maintained as a permanent record.