Systematic reviews provide a comprehensive and unbiased method for retrieving and synthesizing relevant research to answer a specific question. To fully understand what is entailed in conducting a systematic review, it helps to see where it falls in the hierarchy of evidence. The hierarchy or levels of evidence is a central tenet of evidence-based practice and attempts to answer the question, "What is the best evidence?"
Below is a visual representation of the hierarchy of evidence:
As you move up the pyramid, the studies are more rigorous in their design and methodology, which means more quality control is applied increasing their reliability and validity. The systematic review (SR) falls near the top of the pyramid with the Cochrane Systematic Reviews right at the apex.
Primary sources are original studies, which are based on direct observation, use of statistical records, interviews, focus groups or experimental methods. They are authored by researchers, contain original research data, and are usually published in a peer-reviewed journal. Primary literature may also include conference papers, pre-prints, or preliminary reports. The types of primary research associated with EBP are:
However, the quantity of primary studies on a single topic can be overwhelming. How do you find the best articles when there are 400 hits? Secondary literature offers a filter for capturing the best of primary studies and often synthesizes the results for consumers like health care and social work practitioners. Secondary studies include:
The purpose of a systematic review is to sum up the best available research on a specific question. This is done by synthesizing the results of several studies. It is not always possible or ethical to conduct randomized controlled trials (RCTs) in social, health, and human services, so social work traditionally relies on case studies, qualitative analysis, historical inquiries, narrative literature reviews, surveys, and practice guidelines.
