The advent of evidence-based practice (EBP) in the early 1990s has seen the role of the health library and information worker in the ascendancy, with clinicians increasingly relying on health care literature in their decision making. With their knowledge of information sources and their skills to retrieve information to inform health care decisions, library and information sector workers have played,1 and indeed continue to play, an important role in assisting in the uptake of EBP principles and practice. It quickly became apparent that synthesized summaries of ‘all’ evidence within a particular domain would be required, in addition to the evidence from primary studies, if clinicians were to make truly informed decisions within a typical consultation. However, the review article of the time seemed ill-equipped to meet such a challenge. Medical review articles of the pre-EBP era were generally unsystematic and lacked formal statistical methods to derive best estimates of treatment effects from the available information. Consequently, they tended to reach conclusions that were biased and wrong.2
Archie Cochrane, a famous British epidemiologist, noted:
‘It is surely a great criticism of our profession that we have not organized a critical summary, by specialty or subspecialty, adapted periodically, of all relevant randomized controlled trials.’3
In answer to this challenge, the worldwide Cochrane Collaboration was formed in 1992 to provide an expanding resource of updateable systematic reviews of randomized controlled trials (RCTs) relating to health care. Thus began the modern incarnation of the review article, a tool that had for many centuries been the mainstay for updating scientific knowledge.
Rise of the review
While it is well established that, in the 18th century, James Lind was the instigator of the first reported RCT, a lesser-known fact records that he was probably the first to describe the systematic review method. Six years after his first RCT was published,4 Lind wrote:
‘As it is no easy matter to root out prejudices ... it became requisite to exhibit a full and impartial view of what had hitherto been published on the scurvy ... by which the sources of these mistakes may be detected. Indeed, before the subject could be set in a clear and proper light, it was necessary to remove a great deal of rubbish.’5
Gathering research, getting rid of rubbish and summarizing the best of what remains captures the essence of the science of systematic review. Nevertheless, although the need to synthesize research evidence has been recognized for well over two centuries, it was not until the 20th century that researchers began to develop explicit methods for this form of research. A fuller account of the rise of the discipline of research synthesis has been published by Iain Chalmers and other distinguished proponents.6 Recent years have seen recognition that the typical timescale commanded by the rigour of the systematic review process may be unsuited to the decision-making windows available to most policymakers. The need to trade off rigour and relevance has become a central theme to recent methodological developments and has led to a bewildering plethora of review designs developed to meet a variety of demands from the domains of research and policy.
An early example of a review was published in the non-health library and information sector,7 whilst the early 1980s saw the first of many manuscripts seeking to answer the eternal question of how best to undertake bibliographic instruction in the health sciences.8
Coinciding with the first Evidence-Based Library and Information Practice (EBLIP) conference in 2001, Booth proposed that the library and information science (LIS) sector could follow the trend within medical EBP by graduating to the development of more systematic reviews once a critical mass of rigorous studies has been attained.9 A recent evaluation of the evidence base has continued to sound such a call for establishing a solid evidence base within the LIS sector.10
To ‘review’ has been defined as: ‘To view, inspect, or examine a second time or again’.11
This definition broadly characterizes all review types now in existence. What remain largely unacknowledged are the subtle variations in the degree of process and rigour within the multifarious review types. Such variations are most clearly evidenced in the structures and methodologies that distinguish one review type from another. As more professions have adopted and adapted the systematic review method, the LIS sector, as elsewhere, has been afforded access to an ever-increasing variety of methods and techniques for summarizing the evidence base. The model of the systematic review of randomized controlled trials has limited potential within the LIS literature, given that no more than a score of such studies had been identified. This has necessitated the identification of a greater range of review types, opening up the prospect of summarizing case studies, qualitative research and even theoretical and conceptual published and unpublished outputs.
Different types of reviews
Analysis of download statistics from the Health Information and Libraries Journal electronic archive since 2006 indicates that reviews figure prominently amongst the most highly sought articles. This suggests that, as with medicine before it, the LIS sector values the opportunity to access already synthesized evidence in informing its practice. Indeed, in 2008, Ankem noted that there was evidence of systematic reviews making a ‘substantial contribution to medical library and information literature’.12
Ankem, in an evaluation of methods in systematic reviews and meta-analyses published between 1996 and 2006 in the library and information science sector, identified a total of eight manuscripts. These manuscripts, combined with reviews published in Health Information and Libraries Journal following an editorial commitment in 2007 to seek to publish a review in each future issue,13 provide an illuminating insight into the flourishing terminology synonymous with this genre. This terminology includes such terms or phrases as review of the evidence,14,15 comprehensive review,16 literature review,17 overview18 and systematic review.19–30 Given the importance evidence-based practice places upon the retrieval of appropriate information, such diverse terminology could, if unchecked, perpetuate a confusion of indistinct and misapplied terms.