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Systematic Reviews & Meta-Analysis

Systematic reviews and meta-analysis are situated at the top of what is known as the “Evidence Pyramid” (see figure below). As you move up the pyramid the amount of available literature on a given topic decreases, but the relevancy and quality of that literature increases. Systematic reviews and meta-analysis are considered to be the highest quality evidence on a research topic because their study design reduces bias and produces more reliable findings. However, you may not always be able to find (or need to find) the highest level of evidence to answer your research question. In the absence of the best evidence, you then need to consider moving down the pyramid.

Systematic Reviews

A systematic review is a high-level overview of primary research on a particular research question that systematically identifies, selects, evaluates, and synthesizes all high quality research evidence relevant to that question in order to answer it. In other words, it provides an exhaustive summary of scholarly literature related to a particular research topic or question. A systematic review is often written by a panel of experts after reviewing all the information from both published and unpublished studies. The comprehensive nature of a systematic review distinguishes it from traditional literature reviews which typically examine a much smaller set of research evidence and present it from a single author’s perspective. Systematic reviews originated in the biomedical field and currently form the basis of decision-making in Evidence-Based Treatment (EBT) and evidence-based behavioral practice (EBBP).  

For additional information, read the Systematic Reviews entry in the e-reference book The A-Z of Social Research.

Meta-Analysis

Systematic reviews often use statistical techniques to combine data from the examined individual research studies, and use the pooled data to come to new statistical conclusions. This is called meta-analysis, and it represents a specialized subset of systematic reviews. Not all systematic reviews include meta-analysis, but all meta-analyses are found in systematic reviews. Simply put, a systematic review refers to the entire process of selecting, evaluating, and synthesizing all available evidence, while the term meta-analysis refers to the statistical approach to combining the data derived from a systematic-review. Conclusions produced by meta-analysis are statistically stronger than the analysis of any single study, due to increased numbers of subjects, greater diversity among subjects, or accumulated effects and results. Meta-analyses have become common in the social and biomedical sciences. However, some challenge the validity of meta-analysis, arguing that combining data from disparate studies produces misleading or unreliable results.

For additional information, read the Meta-Analysis entry in e-reference book The Concise Corsini Encyclopedia of Psychology and Behavioral Science.

Finding Systematic Reviews & Meta-Analysis

Since there are far fewer systematic reviews and meta-analysis than most other types of research, you will often need to broaden your search terms when searching in the Library’s Databases or the Internet. Also, keep in mind that the term "systematic review" originated in the medical field, so you can expect to see the majority of articles related to medical areas and conditions.

Locating systematic reviews and meta-analysis is extremely beneficial not only because they provide high-quality evidence, but also because they will include extensive references to primary studies relevant to your research topic.

Library Databases & Journals

MEDLINE with Full Text
MEDLINE provides authoritative medical information on medicine, nursing, dentistry, veterinary medicine, the health care system, pre-clinical sciences, and much more. To limit your results to systematic reviews, select “Systematic Reviews” within the Subject Subset box (as shown below) and then type your search terms into the search box.

CINAHL with Full Text
CINAHL allows you to limit your publication type not only systematic reviews or meta analyses, but also to a "meta synthesis." This publication type value is applied to articles that indicate the presence of a qualitative methodology that integrates results from a number of different, but inter-related studies. To limit your results, select “Systematic Reviews” (or Meta Analysis or Meta Synthesis) within the Publication Type box (as shown below) and then type your search terms into the search box.



Alternatively, you may wish to limit your CINAHL search results to Evidence-Based Practice, as shown below. Applying this limiter allows you to limit results to: articles from evidence-based practice journals; articles about evidence-based practice; research articles (including systematic reviews, clinical trials, meta analyses, etc.) and commentaries on research studies (applying practice to research). Selecting Evidence-Based Practice will produce a broader set of results than applying a single publication type limiter.



PsycINFO
Compiled by the American Psychological Association (APA), PsycINFO covers all aspects of psychology, plus the behavioral aspect of education, medicine, sociology, law, management and other fields. To limit your PsycINFO search results to systematic reviews, select “Systematic Review” within the Methodology box (as shown below) and then type your search terms into the search box.

Roadrunner Search
Roadrunner is a great starting point for your research as it searches approximately 95% of the library’s database content, including articles, e-books and videos. To include systematic reviews in your Roadrunner search results, include the phrase “systematic review” in one of the search boxes and change the drop-down menu to TI Title (as shown below).

Systematic Reviews (Journal)
Browse articles covering systematic review products, review protocols, systematic reviews related to a very broad definition of health, rapid reviews, updates of already completed systematic reviews, and methods research related to the science of systematic reviews, such as decision modeling. (2012-present)

Systematic Reviews in Pharmacy (Journal)
Journal provides full length reviews related to different subjects in pharmacy and that are of broad readership interest to users in industry, academia, and government. (2010-present)

Web of Knowledge
Web of Knowledge provides access to current and retrospective bibliographic information, author abstracts, and cited references in social science journals that cover more than 50 disciplines. Note there is no full-text within this database. To include systematic reviews in your Web of Knowledge search results, enter your topic keyword on the top line for Topic. On the second line, type “systematic review” and change the drop-down box to Title (as shown below).



Internet Resources

Campbell Systematic Reviews
Campbell Systematic Reviews is a bimonthly peer-reviewed publication with follows structured guidelines and standards for summarizing the international research evidence on the effects of interventions in crime and justice, education, international development, and social welfare.

Center for Evidence-Based Crime Policy 
Provides systematic reviews on policing, specifically designed and formatted to appeal to law enforcement practitioners and stakeholders.

Center for Evidence-Based Dentistry
The American Dental Association’s collection includes over 2,000 systematic reviews relevant to healthcare in dental settings.

The Cochrane Library
Cochrane provides systematic reviews of primary research in human health care and health policy, and are internationally recognized as the highest standard in evidence-based health care. Each Cochrane Review is a peer-reviewed systematic review that has been prepared and supervised by a Cochrane Review Group (editorial team) in The Cochrane Collaboration.

Database of Abstracts of Reviews of Effects (DARE)
DARE contains details of systematic reviews that evaluate the effects of healthcare interventions and the delivery and organization of health services. DARE also contains reviews of the wider determinants of health such as housing, transport, and social care where these impact directly on health, or have the potential to impact on health.

Database of Promoting Health Effectiveness Reviews (DoPHER)
DoPHER is unique in its focused coverage of systematic and non-systematic reviews of effectiveness in health promotion and public health worldwide. This register currently contains details of over 2,500 reviews of health promotion and public health effectiveness.

Evidence for Policy and Practice Information and Co-ordinating Centre (EPPI-Centre)
Part of the Social Science Research Unit at the Institute of Education, University of London, this site provides a large number of systematic reviews in the fields of Education, including Initial Teacher Education (ITE), Health Promotion and Public Health, as well as social welfare and international development.

Health Evidence
Provides access to over 3,000 quality-rated systematic reviews evaluating the effectiveness of public health interventions. 

NREPP Systematic Review Library
The National Registry of Evidence-based Programs and Practices site provides systematic reviews on topics related to (1) mental health treatment and promotion, and (2) substance abuse treatment and prevention.

Nutrition Evidence Library
The U.S. Department of Agriculture site specializes in conducting systematic reviews to inform Federal nutrition policy and programs.

OTseeker
OTseeker is a database that contains abstracts of systematic reviews, randomized controlled trials and other resources relevant to occupational therapy interventions.

Physiotherapy Evidence Database (PEDro)
Produced by the Centre for Evidence-Based Physiotherapy at The George Institute for Global Health, PEDro is a free database of over 25,000 randomized trials, systematic reviews and clinical practice guidelines in physiotherapy.

PROSPERO
PROSPERO is an international database of over 2,000 prospectively registered systematic reviews in health and social care.

PubMed
PubMed systematic reviews cover a broad set of articles that build consensus on biomedical topics and medical genetics. PubMed also includes meta-analyses, reviews of clinical trials, evidence-based medicine, consensus development conferences, and guidelines. After doing your search, click on the “Article types” limit at the top of the left-hand column and select “Systematic Reviews.”

Note that this Systematic Reviews filter in PubMed will include meta-analyses results. If however, you want to search for only for meta-analyses, select the Meta-Analysis filter under Article Types. You will need to deselect everything in this filter except meta-analyses. Alternatively, you can also search for systematic reviews in PubMed by clicking on the Clinical Queries link on PubMed’s home page.

PubMed Health
PubMed Health specializes in systematic reviews of clinical effectiveness research.

Tutorials & Guides

Finding Systematic Reviews at PubMed Health

How to Cite Cochrane Reviews in APA Style

How to use The Cochrane Library

PubMed: Find Systematic Reviews

Study Design 101 from the The Himmelfarb Health Sciences Library

What is a Systematic Review?

Articles & Books

Biondi-Zoccai, G., Lotrionte, M., Landoni, G., & Modena, M. (2011). The rough guide to systematic reviews and meta-analyses. HSR Proceedings in Intensive Care & Cardiovascular Anesthesia, 3(3), 161-173.

Borenstein, M., Hedges, L. V., Higgins, J., & Rothstein, H. R. (2009). Introduction to meta-analysis. Hoboken, NJ: John Wiley & Sons.

Davis, J., Li, C., & Leucht, S. (2009). Meta-analysis. In R. Mullner (Ed.), Encyclopedia of health services research. (pp. 765-769). Thousand Oaks, CA: SAGE Publications, Inc.

Egger, M., Smith, G. D., & Altman, D. G. (Eds.). (2008). Systematic reviews in health care: Meta-analysis in context. Chichester, GBR: BMJ Publishing Group.

Garg, A., Hackam, D., & Tonelli, M. (2008). Systematic review and meta-analysis: when one study is just not enough. Clinical Journal Of The American Society Of Nephrology: CJASN, 3(1), 253-260.

Glasziou, P., Irwig, L., Bain, C., & Colditz, G. (2001). Systematic reviews in health care: A practical guide. Port Chester, NY: Cambridge University Press.

Gough, D., Oliver, S., & Thomas, J. (2012). Introducing systematic reviews. In D. Gough, S. Oliver & J. Thomas (Eds.), An Introduction to Systematic Reviews (pp. 1-16). Los Angeles, CA: SAGE Publications, Inc.

Hernandez, A. (2009). Meta-analysis and literature review. In M. Kattan (Ed.), Encyclopedia of medical decision making. (pp. 763-768). Thousand Oaks, CA: SAGE Publications, Inc.

Neely, J., Magit, A. E., Rich, J. T., Voelker, C. J., Wang, E. W., Paniello, R. C., & ... Bradley, J. P. (2010). A practical guide to understanding systematic reviews and meta-analyses. Otolaryngology-Head & Neck Surgery, 142(1), 6. doi:10.1016/j.otohns.2009.09.005

Rudnicka, A., & Owen, C. (2012). An introduction to systematic reviews and meta-analyses in health care. Ophthalmic & Physiological Optics, 32(3), 174-183. doi:10.1111/j.1475-1313.2012.00901.x

Sharland, E. (2012). Systematic review. In M. Gray, J. Midgley, & S. Webb (Eds.), The SAGE handbook of social work. (pp. 482-499). London, United Kingdom: SAGE Publications, Inc.

Sirin, S. (2010). Meta-analysis. In N. Salkind (Ed.), Encyclopedia of research design. (pp. 794-799). Thousand Oaks, CA: SAGE Publications, Inc.

Uman, L. (2011). Systematic reviews and meta-analyses. Journal of the Canadian Academy of Child and Adolescent Psychiatry, 20(1), 57-59.

Webb, C., & Roe, B. H. (Eds.). (2008). Reviewing research evidence for nursing practice: Systematic reviews. Malden, MA: Blackwell.

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