It is generally agreed that practice should be based on the current best evidence. However, in order to achieve this, we need to know what the current best evidence is. Literature review methodology can be a useful part of establishing this.
Not all the evidence that exists is good evidence, so it is necessary to evaluate any evidence that we find, or are presented with, in order to determine how much heed should be paid to it. In addition, there is often more than one piece of evidence on a given subject, and the actions recommended across sources are not always consistent. Finally, some evidence is perfectly good for what it claims to be, but is not sufficient, of itself, to really convince us that it should be acted on. Therefore, in order for our practice to be directed by the current best evidence, all the existing information on a subject needs to be identified, evaluated and synthesized so that the nature and strength of that evidence when viewed as a whole is known.
Despite the desirability of identifying the current composite best evidence in this way, the ever-increasing body of literature related to health and social care can make it very difficult for individual practitioners to achieve in any field of practice (Uman 2011). Good quality reviews of the existing literature, that provide a rigorously derived summary of what is and is not currently known about a subject, and the strength of the evidence that exists, can therefore be very useful. Nonetheless, like any evidence, in order to be useful, such reviews must themselves be of good quality. One intention of this book is to explore, step by step, the process of using literature review methodology to conduct a rigorous review of the existing literature on a particular subject. First, though, what a study that uses literature review methodology is requires clarification.
1.1 What is a literature review?
A literature review is exactly what the name suggests: a review of the existing literature on a subject. However, the term encompasses a number of different types of review, ranging from essays that do not claim to be particularly rigorous or systematic, through to systematic reviews (Aveyard 2014: 2ā3). All of these approaches gather and present existing literature on a particular subject. However, the level of rigour with which reviews are conducted, and whether their intention is to identify, analyse and collate all the existing literature on a specific topic, varies, depending upon the type of review in question.
At the top end of the quality scale of reviews of the literature in terms of rigour and system are systematic reviews, such as those published by the Cochrane Collaboration. These are high-quality reviews of all the available evidence on a subject (Aveyard 2014: 2ā3). They systematically and exhaustively search for and evaluate all the available evidence on the subject in question, including the unpublished literature, and articles that are not in the reviewersā first languages. The studies for inclusion in the review are selected using predefined eligibility criteria, and the review is conducted using a clearly stated and reproducible methodology (Higgins and Green 2011). This type of review is generally undertaken by a team of researchers and requires considerable time and resources (Aveyard 2014: 2ā3). At the other end of the spectrum in terms of the required level of rigour and system are documents that are described as literature reviews, but are really essays in which some of the literature on a subject is presented. Such reviews do not claim to follow a rigorous or systematic process, or to include all the literature related to the subject in question.
Studies that use literature review methodology fall somewhere between the two types of review described above. They aim to critically evaluate the existing evidence on a subject and to develop a narrative that presents the composite best evidence concerning this (Roberts and Bailey 2010). However, they are not required to be as exhaustive as a systematic review (for example, there is generally no expectation that literature in languages that the reviewer does not speak will be accessed and translated). This is in part because studies that use literature review methodology do not necessarily have a team of researchers involved: often, they are the work of a sole person, with limited funding. There are many situations in which this type of review can be very valuable. For instance, an individual or small team may want to evaluate and collate the existing evidence about something relevant to their day-to-day practice, but may not have the time or resources to conduct a full systematic review. In such situations, literature review methodology can be used to carry out a smaller scale, less exhaustive, but still systematic and rigorous, review of the current evidence regarding a particular issue (Cronin et al. 2008; Roberts and Bailey 2010; Aveyard 2014: 2ā3).
1.2 Literature review methodology as secondary research
Because it is designed to be a rigorous and systematic form of enquiry, literature review methodology can be described as a form of secondary research. The distinction between primary and secondary research is that in primary research original data are collected and analysed (Aveyard 2014). In contrast, in secondary research, data that have already been collected and analysed are gathered, in order to explore what the existing evidence shows when seen as a composite whole. In effect, literature review methodology therefore uses existing literature as its data. However, to earn the title of secondary research, a literature review must meet the quality standards of research: it must follow a process that is systematic, rigorous, and minimizes the risk of the apparent findings being due to chance, errors or bias (Cronin et al. 2008, Aveyard 2014: 3ā4). In order to achieve this, several discrete steps should be followed when carrying out a study using literature review methodology, as shown in Box 1.1. Each stage is equally important in ensuring that the process as a whole is rigorous and systematic. The rest of this book describes and discusses these stages of What is literature revieW methodology?the literature review process.
Box 1.1
Steps required in a study that uses literature review methodology
ā¢ Identify the need for a review.
ā¢ Determine the focus of the review.
ā¢ Devise the review question, aims and objectives.
ā¢ Develop the search strategy.
ā¢ Formulate clear inclusion and exclusion criteria.
ā¢ Carry out the search.
ā¢ Record details of the search, the documents retrieved and the decisions made about their inclusion or exclusion from the review.
ā¢ Appraise each individual piece of evidence.
ā¢ Synthesize the findings from across all the evidence.
ā¢ Draw conclusions.
ā¢ Make recommendations.
ā¢ Consider ways in which to disseminate the findings from the review.
1.3 Overview of the book
The remainder of this book is divided into two parts: the first explores the context and background of literature review methodology: some of the reasons why a literature review might be conducted, and the characteristics of a good review. The second part deals with the process and practicalities of conducting a study that uses literature review methodology.
In the first part of the book, Chapter 2 discusses some of the circumstances in which conducting a literature review can be useful, including both practice-based and academic situations. The chapter is divided into three main sections: first, carrying out a literature review to fulfil some of the requirements of a programme of study; second, carrying out a literature review because of a problem that has been identified in practice and, finally, carrying out a literature review to support and further develop an area of good practice.
Having identified in Chapter 2 some of the circumstances in which using literature review methodology might be useful, Chapter 3 provides an overview of what constitutes a good quality review of the literature. This chapter focuses on the need for the study as a whole to be systematic, rigorous, unbiased, and for the rationales for the decisions made to be explicit. However, it also highlights the purpose and importance of each of the key stages within a study that uses literature review methodology. These stages then form the individual chapters of the second part of the book.
In the second section of this book, the individual methodological steps required to conduct a good quality review of the literature are discussed, with one chapter devoted to each step.
Chapter 4 addresses the background to, and rationale for, carrying out a review of the literature. It outlines how the documentation of the background reading that informs the development of the review question differs from the in-depth evaluation of the existing evidence that constitutes the main body of the review. It also discusses the type of information that might be incorporated in the background and rationale sections of a review, and how they can be structured so as to lead logically to the reviewās question and aims.
Chapter 5 focuses on the development of the reviewās question, aims and objectives. It discusses the importance of having a clear, focused and answerable question, how this can be achieved, and the consequences of it not being accomplished. It then explores the development of aims that will enable the review question to be answered, and that are realistic and achievable. The chapter goes on to differentiate the aims of the review from its objectives, describing the value of having specific objectives, but the need for these to be congruent with the study question and aims.
Chapter 6 outlines the process of conducting a search for evidence that will address the reviewās question and aims, including the development of a search strategy, and the practicalities of carrying out a search. It discusses ways of breaking the study question into key concepts, including the use of tools such as PICO, SPICE and SPIDER to achieve this. It then goes on to describe the process of identifying keywords and their synonyms, using Boolean operators, truncation and wildcards, and the importance of having clear inclusion and exclusion criteria for the review. This is followed by an exploration of the decisions that need to be made regarding how to source literature, and the types of literature that will be included in the review. Finally, the practicalities of conducting the search, recording the results of the search, and steps that can be taken if the initial search yields inadequate or excessive numbers of papers are discussed.
Chapter 7 explores the next stage in the literature review process: appraising the literature that has been gathered for review. It begins with an explanation of the importance of this step being systematically and rigorously undertaken, and the value of using specifically designed tools to assist in achieving this. The chapter then discusses the general principles of appraising research, before entering into an exploration of the particulars of appraising qualitative, quantitative and mixed methods research. The chapter ends by discussing how other forms of evidence such as evaluation, audit, expert opinion and case reports can be appraised.
Chapter 8 moves on from the process of appraising each individual piece of evidence included in the review to a discussion of the process of synthesizing the evidence from across sources. It begins with an overview of some of the approaches that can be used for the synthesis of qualitative, quantitative and mixed methods studies, such as meta-analysis and meta-synthesis. However, these types of synthesis are often not appropriate for a study that uses literature review methodology. Therefore, the main focus of the chapter is on narrative approaches to the synthesis of evidence from sources that are heterogeneous, and potentially include both research and non-research evidence.
Chapter 9 takes the process of literature review methodology to the stage beyond the findings from the review, to the discussion of these findings. It outlines the purpose of the discussion section of a study that uses literature review methodology, and explores what should be What is literature revieW methodology?included in it. It also highlights how the discussion of the findings from the review should enable these to be distinguished from, but also located within, the existing body of evidence on the subject in question.
Chapter 10 explores the final element of a study that uses literature review methodology: the drawing of conclusions and making of recommendations. It outlines the need to ensure that the conclusions are derived from the findings, that they are clearly stated, answer the initial study question, and address its aims. The chapter then discusses the making of recommendations from the literature reviewās findings, emphasizing the need for there to be a clear relationship between the study question, aims, findings, conclusions and recommendations.
Chapter 11 goes beyond the final stage of conducting a study that uses literature review methodology, by discussing approaches to disseminating the findings from the review. In this chapter, the value of sharing the findings from a review of the literature is outlined, followed by ways in which this may be achieved, including publication, conference...