Systematic review searching

From UBC Health Library Wiki

Another view of the "evidence wedge"

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Introduction

see also: Expert searching, Filters (ie. hedges), Hand-searching and Scoping studies

"Systematic reviews seek to identify as many potentially relevant studies as possible that meet the research question for a given topic."

The purpose of a systematic review is to collect ALL available evidence whether it is in the peer-reviewed, indexed literature or published on the web outside of regular publishing channels (in the grey literature). Systematic reviews (SRs) are often described as 'papers that summarize other papers' and defined as "overviews of primary studies that have used explicit and reproducible methods". Typically, SRs synthesize findings from important clinical trials that may or may not include a meta-analysis. In information retrieval for the SR, it is important to document search strategies and ensure reproducibility.

Consultation with a health librarian

Even though health librarians play a key role in cumulating evidence for the systematic review, searching is also done by the researchers themselves with health librarians assuming consultation roles as retrieval experts. However, several issues must be considered when this type of consultative work is undertaken. Efficient retrieval plays a significant (and central) role in answering clinical questions and in the gathering of evidence for a SR. At the initial stages of finding best evidence, it is crucial that relevant studies are found and that multiple sources are searched (including those considered to be in the deep or hidden web or known as grey literature). Your goal as an information retrieval specialists or expert searcher is to maximize recall and to minimize the bias in doing so. Comprehensive searching for all relevant studies is critical as is the documentation of explicit strategies. You may need to consult a health librarian about your searches. Keep in mind that you must carefully document and report your search strategies. Hand-searching and snowballing are required as is searching for the grey literature. The latter involves techniques that help in locating additional studies not indexed in databases such as MEDLINE or Embase.

Search strategies

SRs are scientific investigations in themselves, with pre-planned methods and an assembly of original studies as their "subjects." They synthesize the results of many primary studies by using strategies to limit bias and error. However, no study or investigation can occur unless an information specialist has reviewed your searches or helped in their formation.

In summary, the role of the SR searcher is to:

Understand systematic review methods
Plan search strategies
Undertake faceted searching using various tools, engines and databases
Be able to locate and use methodological search filters
Understand how to do budgeting and cost support for research grants
Be able to document search processes, and work towards reproducibility
Have an awareness of managing references using RefWorks
Understand the importance of searching in the systematic review process

For an excellent overview of expert search strategies, see Evidence for Policy and Practice Information and Co-ordinating Centre (EPPI-Centre).

Scoping the search

see also Rapid evidence-assessments (REAs) and Scoping studies

Preparation may involve literature scoping searches or doing literature reviews for clinical teams. Scoping searches are typically done to locate existing SR and major randomized clinical trials. The results from these initial scoping searches provide further focus (or refocus) for the direction of proposed research. There is little need to replicate studies that have been registered as a protocol at the Cochrane Library or elsewhere. Scoping searches are done in major databases such as the Cochrane Library, MEDLINE, CINAHL, Google scholar and PsycINFO. They involve a refining process and identifying what information sources should be searched thoroughly. Full literature searching aimed at retrieving a maximum number of relevant studies or articles in a given discipline starts with a scoping review. The scoping process is iterative and helps to estimate the size of the literature in question, and the estimated costs of searching it. Some health librarians are beginning to offer their information retrieval skills for rapid evidence-assessments (REAs) because interdisciplinary search topics increase the likelihood of time-consuming and expensive searching, and it may be important to know this before a large-scale project is undertaken. Arksey and O'Malley in 2005 outline a methodological framework that identifies different types of scoping studies, and how these compare to systematic reviews. Identifying key, searchable sources of information is a process that varies considerably depending on the research or clinical question. The best tools and searching protocols are devised accordingly, but searching for systematic reviews requires search tracking far beyond scoping. Searching in the top five or ten biomedical databases is not enough; additional resources must be identified, even non-English materials, and the grey literature. Some sources of information are well-developed and stable, but others hidden in the deep web are not.

Search filters

see also Filters (ie. hedges)

"A search term or terms (such as 'random allocation' for sound studies of medical intervention) that select studies that are at the most advanced stages of testing for clinical application." (Haynes RB, Wilczynski N, McKibbon 1995, p436)

Search filters - also hedges, optimal search strings or clinical queries -- are predefined strategies designed to retrieve high levels of evidence (ie. randomized controlled trials, meta-analysis or systematic reviews) and/or articles that discuss clinical queries (diagnosis, prognosis, etiology, treatment). Search filters are called 'methodological' strategies because they consist of terms that relate to study design. RCT filters, for example, contain terms such as double blinded, randomized, clinical trial. Diagnosis filters contain terms such as sensitivity, specificity, and so on. While (RCTs) are achievable in clinical settings public health interventions can rarely replicate the controlled environment of the clinic. Researchers, policy-makers and decision-makers often rely on other types of study designs for evidence. There is currently no standard model for synthesizing results of studies that do not have controls. Synthesis methods, critical appraisal tools and studies that deal with appraising and synthesizing quantitative studies without control groups are needed; precautions when including non-controlled studies as evidence are also needed. (For more information, see Fitzpatrick-Lewis D et al. Methods for the Synthesis of Studies without Control Groups.)

Expert searches

see also: Expert searching

After research questions and search strategies are determined, exhaustive searches can be carried out to provide as thorough a list of studies as possible both published and unpublished, which may fit the inclusion criteria and hence be suitable. Expert searching for SRs is generally considered the province of health librarians. SR search specialists should be consulted during the early stages of planning as they are trained to search efficiently and stay current with information trends. Health librarians help to locate documents from the deep web and assist in formatting references using citation management tools. Some librarians specializing in expert searching often work in hospital or university libraries; others work outside traditional contexts nearer established research institutes, epidemiology groups, technology assessment programs, and other clinical research programs. Some are entrepreneurial and work on a contract basis with various health groups.

Systematic review searching

From UBC Health Library Wiki

Contents

Introduction

Consultation with a health librarian

Search strategies

Scoping the search

Search filters

Expert searches

References

Views

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