"Systematic reviews require a thorough, objective and reproducible search of a range of sources to identify as many eligible studies as possible" (Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.0 (updated July 2019). Cochrane, 2019. Available from www.training.cochrane.org/handbook).
The five steps in a systematic review
Step 1: Framing questions for a review
The problems to be addressed by the review should be specified in the form of clear, unambiguous and structured questions before beginning the review work. Once the review questions have been set, modifications to the protocol should be allowed only if alternative ways of defining the populations, interventions, outcomes or study designs become apparent
Step 2: Identifying relevant work
The search for studies should be extensive. Multiple resources (both computerized and printed) should be searched without language restrictions. The study selection criteria should flow directly from the review questions and be specified a priori. Reasons for inclusion and exclusion should be recorded
Step 3: Assessing the quality of studies
Study quality assessment is relevant to every step of a review. Question formulation (Step 1) and study selection criteria (Step 2) should describe the minimum acceptable level of design. Selected studies should be subjected to a more refined quality assessment by use of general critical appraisal guides and design-based quality checklists (Step 3). These detailed quality assessments will be used for exploring heterogeneity and informing decisions regarding suitability of meta-analysis (Step 4). In addition they help in assessing the strength of inferences and making recommendations for future research (Step 5)
Step 4: Summarizing the evidence
Data synthesis consists of tabulation of study characteristics, quality and effects as well as use of statistical methods for exploring differences between studies and combining their effects (meta-analysis). Exploration of heterogeneity and its sources should be planned in advance (Step 3). If an overall meta-analysis cannot be done, subgroup meta-analysis may be feasible
Step 5: Interpreting the findings
The issues highlighted in each of the four steps above should be met. The risk of publication bias and related biases should be explored. Exploration for heterogeneity should help determine whether the overall summary can be trusted, and, if not, the effects observed in high-quality studies should be used for generating inferences. Any recommendations should be graded by reference to the strengths and weaknesses of the evidence
Khan, K. S., Kunz, R., Kleijnen, J., & Antes, G. (2003). Five steps to conducting a systematic review. Journal of the Royal Society of Medicine, 96(3), 118–121. https://doi.org/10.1258/jrsm.96.3.118
What is PRISMA? The PRISMA statement is an evidence-based set of items for transparent reporting in systematic reviews and meta-analyses. You can find out more information on how to incorporate PRISMA into your research on their website.
Step 1: Preparation To complete the the PRISMA diagram print out a copy of the diagram to use alongside your searches. It can be downloaded from the PRISMA website. You will need to print a copy with totals from all the databases, but you may want to print out a copy for each database you search as well. If you are using this system for a more advanced assignment, ask your supervisor whether they would like you to follow this system, or to specify totals for each individual database in your final PRISMA diagram.
Step 2: Doing the database search For each database enter each key search term individually. This should include ALL your search terms, including MeSH or other subject headings, truncation (like hemipleg*), and/or wildcard (like sul?ur) search terms. Combine all the search terms in the different combinations using boolean operators like AND or OR as appropriate. Apply all your limits (such as years of search, English language only, and so on). Once all search terms have been combined and you have applied all relevant limits, you should have a number of records or articles. Enter this in the top left box of the PRISMA flow chart for each database. If you have searched databases individually, add all the 'records identified' up and fill this total number in the PRISMA flow diagram which you will use for your coursework. Remember this process of adding up the number of records in individual database searches to a total will need to be repeated at each step if you search databases separately.
Step 3: Additional sources If you have identified articles through other sources than databases (like manual searches through reference lists of articles you have found or Search engines like Google Scholar), enter the total number of records in the box on the top right of the flow diagram.
Step 4: Remove all duplicates To avoid reviewing duplicate articles, you need to remove any articles that appear more than once. You will need to go through all the records or articles you have found in the database and manually remove any duplicates. This is not easy to do if you have a large number of articles at this point. In this case you may want to export the entire list of articles to a citation manager such as EndNote, Sciwheel, Mendeley, or Zotero (including both citation and abstract in your file) and remove the duplicates there. Enter the number of records left after you have removed the duplicate in the second box from the top.
Step 5: Screening articles The next step is to add in the number of articles that you have screened. This is the same number as you have entered in the duplicates removed box.
Step 6: Screening - Excluded articles You will now need to screen the titles and abstracts for articles which are relevant to your research question. Any articles that appear to help you provide an answer to your research question should be included. Record the number of articles excluded based on this screening process in the appropriate box (next to the total number of screened records) with a short reason for excluding these articles.
Step 7: Eligibility Subtract the number of excluded articles following the screening phase (step 6) from the total number of records screened (step 5) and enter this number in the box titled "Full-text articles assessed for eligibility". Get the full text for these articles to review for eligibility. You can request articles through Interlibrary Loan to ensure you get access to the most research.
Step 8: Eligibility - Records excluded Review all full-text articles for eligibility to be included in the final review. Take a note of the number of articles that you exclude at this point and enter this number in the correct box titled: Full text articles excluded, and then write in a short reason for excluding the articles (this may be the same reason used for the screening phase). Examples include wrong setting, wrong patient population, wrong intervention, wrong dosage, etc.
Step 9: Included The final step is to subtract the number of excluded articles or records during the eligibility review of full-texts (step 8) from the total number of articles reviewed for eligibility (step 7). Enter this number in the qualitative synthesis box. If you perform a meta-analysis, you would also list the number of studies in the quantitative synthesis box, You have now completed your PRISMA flow diagram which you can now include in the results section of your article or assignment.
Below is a selection of print books and ebooks in the collection on systematic reviews and meta-analyses. Hover over the title for a brief overview and click on the title to be taken to the listing in the catalog where you can find more information such as location in the library, call number, and how to access the book if it's online. If you want to find additional print or ebooks, send me an email or ask a librarian around the clock using our Ask Us 24/7 chat service!
Need a book that we don't have in the collection? Borrow it using our interlibrary loan service.
For more information on conducting systematic reviews and meta-analyses, see the online resources below: