Introduction to Meta-Analysis by 
DeduplicatingYour first step after collecting all the results of you searches into EndNote is to deduplicate as you may find the same article downloaded from multiple databases. Use the 'Find Duplicates' option in the 'Library' menu on EndNote. This will show you the duplicates side-by-side so you can choose which one to keep. It won't pick up all duplicates (such as different forms of names), so you will still need to scan down the list of references and move any additional duplicates to trash. Make sure you make a note of the total number remaining in your Library and the number in your trash - you will need these for your PRISMA diagram (Step 7).
Once you have de-duplicated the records in EndNote, you have to evaluate the remaining ones against the inclusion and exclusion criteria (established previously in your protocol). This screening process can be completed in EndNote with references moved to Include/Exclude groups as decisions are made. Alternatively the results can be exported to other software (see below) to manage the screening process.
Read the title and abstract of each study and use your inclusion/exclusion criteria to judge their relevance. Sort them all into an 'Include' or 'Exclude' group. Make a note of the numbers in each group for your PRISMA diagram.
Ideally, each study is screened by two people, and if they make the same decision (Yes or Maybe – include; No – reject) then the study is moved into an Include or Exclude group. If different decisions are made by the screeners - “conflicts” - then a final consensus decision has to be made to move the study into the correct group. Having two screeners at each stage minimises risk of bias, but is not always feasible (especially for students). If you are working as a team, before you start screening, you must have a shared understanding of what counts as relevant. Otherwise you will get constant conflicts. There will always be some conflicts, but normally only a few per cent.
Once you have done your initial screening using the title and abstract you will have excluded the vast majority of articles as being irrelevant. Next you need to get the full text of the articles in your 'Include' group.
EndNote has a 'Find full-text' tool which can automatically find and attach the full PDFs to the references in your 'Include' group. For the ones it can't find search for the article title on Summon (the second search box on the Library homepage) and Google Scholar and manually attach the PDFs to the relevant refences. Any that you can't find can usually be obtained via our inter-library loans service, although there is a limit on the number you can request depending on your status, so you might need to prioritise.
The next step is to read the full text of the ones in your 'Include' group – read until you read an exclusion reason. Sort them into two final groups (e.g. 'Final selection' and 'Final rejection') and record the reasons for exclusion. Reasons can be recorded in EndNote in the research notes or custom fields so that you have a note of them to add in your PRISMA flow diagram. Or just keep a separate record of the reasons and the number excluded for each reason.
Once you have selected the relevant studies you must evaluate their quality as not all will have a sufficiently rigorous methodology to avoid biased results. Use the checklists available via the links below to help you with this task. Your supervisor should also be able to advise you on this aspect of your study.
The Knowledge and Library Services division of the Barts Health NHS Trust have put together this series of short videos on using the CASP checklist to evaluate randomised controlled trials:
See the following links for further help on doing a critical appraisal of the literature:
There are many tools for managing the screening process. You can do this within EndNote, but for larger studies you might want to consider the following tools. Please note that we are unable to offer support for using these products. If registration is required do not use your university password, especially in combination with your university email address. Pick a different, strong and unique password.
Lists of references can be exported from reference management tools such as EndNote into Excel for screening. This is the most basic tool for the job. For a more fully-featured product see Rayyan below.
Rayyan is a free online tool that can be used for screening and coding of studies. It will pre-populate inclusion and exclusion criteria, although these can be customised. You can also tag and filter to code and organize references. Works well for title and abstract screening, for full-text screening revert to EndNote (you can export references from Rayyan back to EndNote for this step). Supports collaboration and blind reviewing to avoid bias. Has an app for use on mobiles and tablets.
This is an online systematic review management tool. The University does not have a licence for it but small teams can purchase individual licences.
Although primarily a tool for qualitative evidence synthesis from interviews, focus groups and open-ended survey questions, NVivo can be used for drawing out themes from literature gathered as part of systematic review. It is possible to download a free trial version for two weeks which can then be fully activated with the University's licence on request from Digital Technology Services (DTS). It is also available to use via AppsAnywhere on campus.
A web-based software program for managing and analysing data in literature reviews. It is suitable for all types of systematic review (meta-analysis, framework synthesis, thematic synthesis etc) but also has features that would be useful in any literature review. It manages references, stores PDF files and supports qualitative and quantitative analyses such as meta-analysis and thematic synthesis. It also contains some ‘text mining’ technology for making systematic reviewing more efficient. Sign up for a month long free trial, subscription fees apply after that.
Data extraction is pulling together the information in the study - the population, methodology, outcomes etc. - so that it can be compared with the same fields of information in the other studies.
For an overview of data extraction tools see this page produced by Cornell University Library: