Which databases should I search when doing a literature review?

First decide what the purpose of your review is.  A systematic review needs to be comprehensive.  The aim of the search is to find ALL the original research that can help to answer the research question.  Other types of review aim to find a representative sample of the papers available, and some reviews aim to retrieve not just primary research but also other forms of evidence. Knowing what type of evidence you want, and how comprehensive you intend the search to be will help you make the decision about where to search.

The next step is to look at what databases are available to you and whether combining them together will allow you to look at all the sources in which your evidence might be found. Each database indexes a certain number of journals, books, conference proceedings and other evidence-your intention is to use databases to reduce gaps in your  search.  You want to look at all the relevant sources but not duplicate too much.

Each database defines its scope, telling you what it includes. Identify the long-list of potential databases by using the library database finder.  Next look at scope note that usually accompanies each of the databases available in the library which will give you enough information to know whether the database is suitable or not.  Next go to the database itself and look at the ‘help’ or ‘search tips’ section, which will give you a little more detail. While you are doing this you can also take note of the type of evidence that is included in the database.  Web of Sciences core collection for example, indexes conference proceedings, abstracts and books as well as journal papers.  In order to retrieve more of what you want and less noise you will need to exclude a number of types of evidence.






What are the types of literature review?

Reviews summarise or integrate/synthesise evidence.  The difference between these two approaches is whether your intention is to describe what is known (summarise) or build something new (integrate/synthesise).  Selecting the type of review you wish to undertake should be based on what you want the outcome of the review to be, the time you have available, and your skill level.  More comprehensive and systematic approaches usually involve experts and teams.

Cooper (1988 cited in Cooper and Hedges 2009) offers a useful overview of the different characteristics that can be used to define review types.


The following sections describe a number of different types of review but is not exhaustive. You are advised to read Pare et al. (2015) for further detail about these types of review.  What you decide to call your review will be based on which type you decide to undertake but you will also supplement your description with the method that you used to analyse the data.  This will be the subject of another blog but for now you should read Dixon-Woods et al. (2005).

Descriptive reviews

A narrative review is not systematic.  These reviews don’t aim to find all the available evidence, they tend to use the evidence that is readily available.  This type of review is usually seen as a component of an academic assignment where the aim is to provide some background. The narrative review because of its lack of systematic identification of evidence, and often a lack of detailed description of the methods used, will be subjective and may be biased.  The aim of the narrative review is to summarise knowledge about a specified topic but the method used means that the summary is likely to be incomplete and descriptive.  This sort of review stops short of interpreting the evidence.

A descriptive review  differs from a narrative review in its intent.  The reviewer gathers evidence more purposefully. The search will be systematic and the evidence used in this form of review will be representative of what is available but incomplete.  The purpose of this type of review is to collate evidence, usually using a quantitative approach, to describe trends or patterns.

Scoping or mapping reviews are often used when the extent of knowledge and evidence available about a specified topic is not known.  The aim is to discover what information is available and therefore the search is comprehensive although often strict date limits are used to make the review feasible.  There is debate about whether the evidence included should be appraised for its quality.

Integrative or synthesising reviews

The following examples of review types are all systematic in nature.  A systematic review is one where the method used is transparent (and reproducible), uses a logical and comprehensive search strategy to gather all relevant research, includes critical appraisal, and synthesises the results of the included studies (EPPI 2017). There is a useful video from the Cochrane collaboration describing systematic reviews.

An integrative review uses a systematic search strategy to identify all the available evidence from a diverse range of sources. It usually gathers primary qualitative and quantitative research as well as theoretical literature (Whittemore and Knafl 2005). An updated perspective on the integrative review is the mixed studies review (Pluye et al. 2009), which is also described as a meta-needs assessment (Gaber 2000), mixed methods review (Thomas and Harden 2005), mixed research synthesis (Sandelowski 2006) or a realist review (Pawson et al. 2005).  Pluye et al. (2009) have suggested the term mixed studies review as a generic and precise term.  They point out that the term integrative review, which is very popular in nursing, midwifery, and allied health professional (NMAHP) work is often applied to reviews that don’t include diverse evidence but often focus on a single approach and don’t include theoretical sources.

The integrative review is often used by students undertaking a dissertation. If you were to use the method described by Whittemore and Knafl (2005) or Pluye et al (2009) you would also have to justify the scope of your search and decisions you made about whether you were including only peer reviewed primary research or other theoretical sources.  Many students also have to justify why they have concentrated only on qualitative or quantitative papers.  Ideally you should search for both.

Meta-analysis uses a systematic and comprehensive search approach and critical appraisal to select suitably rigorous quantitative studies.  The numerical findings are extracted and statistical techniques are used to combine the findings of each paper. The aim of the meta-analysis is to evaluate the consistency of results of different studies, explain differences, and combine the results.  Bringing together the results of a number of smaller studies generates a more powerful study.  Although meta-analyses are important, they can only combine the available information. Publication bias can mean that negative results have not been published and are not included.

qualitative systematic review is very similar to the meta-analysis but uses qualitative studies instead of quantitative.  The reviewers decide before gathering the studies systematically what they will define as ‘data’.  Data can be the original researchers interpretation of their findings and/or any raw data included in the research report (e.g. participant quotes). The synthesis can be both quantitative (e.g. frequency with which a particular issue was raised) and qualitative (e.g. appreciating the meaning of the findings and generating themes that accurately describe those findings).  There are a number of frameworks or analytical approaches that can be used in a qualitative systematic review, which reviewers will use as their named approach.  For example meta-ethnography describes a specific approach to the way that data from each study is analysed.

The realist review moves away from the positivist philosophical position.  A positivist tries to draw a general conclusion from the synthesis of studies.  The positivist believes that we can develop a model that predicts what will happen – if I do X then Y will occur. This works in many situations but not others. For example, if we were to try and understand the impact of school tobacco policies on adolescent smoking behaviour (Schreuders et al. 2017). The realist review looks at complex systems to explore how they work or fail in a specific context (Pawson et al. 2005).

An umbrella review is a review of reviews.  This is often used to bring together the results of a number of systematic reviews.  The review as a research method was developed to help bring together the results of multiple studies published on the same issue and this has led to multiple reviews being published on the same issue.  The umbrella review uses a systematic search process and critically appraises the quality of the reviews that are retrieved before synthesising the results.

The critical review gathers evidence and appraises its quality against a pre-defined set of criteria. The aim of this is to give direction for future work by identifying strengths and weaknesses of the published evidence.  The search strategy is selective rather than comprehensive.

Cooper HM, Hedges LV (2009) Research synthesis as a scientific process IN HM Cooper, LV Hedges, JC Valentine (Eds) The handbook of research synthesis and meta-analysis, 2nd Edn. New York, The Russell Sage Foundation

Cooper HM (1988) Organising knowledge synthesis: a taxonomy of literature reviews Knowledge in Society 1:104-126

Dixon-Woods M, Agarwal S, Jones D, Young B, and Sutton A (2005) Synthesising qualitative and quantitative evidence: a review of possible methods Journal of Health Services Research and Policy 10(1):45-53

EPPI centre: Evidence Informed Policy and Practice (2017) What is a systematic review [online] https://eppi.ioe.ac.uk/cms/Default.aspx?tabid=67 (Accessed 25.10.17)

Grant MJ, and Booth A (2009) A typology of reviews: an analysis of 14 review types and associated methodologies Health Information and Libraries Journal 26:91-108

Pare G, Trudel M-C, Jaana M, Kitsiou S (2015) Synthesizing information systems knowledge: a typology of literature reviews Information and Management 52:183-199

Pawson R, Greenhalgh T, Harvey G, Walshe K (2005) Realist review – a new method of systematic review designed for complex policy interventions Journal of Health Services Research and Policy 10 (Suppl 1): 21-34

Pluye P, Gagnon M-P, Griffiths F, Johnson-Lafleur J (2009) A scoring system for appraising mixed methods research and concomitantly appraising qualitative, quantitative, and mixed methods primary studies in Mixed Studies Reviews International Journal of Nursing Studies 46: 529-546

Schreuders M, Nuyts PAW, den Putte B, Kunst AE (2017) Understanding the impact of school tobacco policies on adolescent smoking behaviour: A realist review Social Science and Medicine 183:19-27

Whittemore R, Knafl K (2005) The integrative review: an updated methodology Journal of Advanced Nursing 52(5): 546-553

Searching – does it ever end?

A number of my students are new to conducting a systematic search and they have found out that this is an iterative process, and one that seemingly has no end.  Here are some tips to help you deal with this frustrating but normal process.

  1. Accept that you will build the search gradually.  No-one gets it right first time.
  2. Learn from each search about additional terms that might improve the results.
  3. Think about whether you need to get rid of some of your terms – do they mean what you think they mean?
  4. Look at other reviews looking at similar issues to you – what terms have they used?
  5. Save each search you conduct so that you can edit and re-run them when you discover additional search terms.
  6. Be methodical
  7. Record the results of searches, the search terms you have used, and the reasons for decision as you go along.

What happens when you find a search term after you thought you had finished?  I have found search terms even during the writing up process.  After some thought I decided that the search wasn’t complete without the new term.  I conducted a search for that term in conjunction with the other key words.  I didn’t do the whole thing again, just focused on the new term and the words that would help me find any papers that were relevant.  I found a couple more papers and was able to plug them into my PRISMA diagram, appraise them, extract their data and adjust my finding.  It wasn’t a big deal because I accept that I won’t get it right first time.

The process does come to an end eventually but it is better to think about it as voyage than a task. This diagram of the process is available on canvas or by email from me (a.swift@bham.ac.uk)

Search strategy

The nightmare of the systematic search…

We introduce searching databases to our nursing students in year 1 of the programme.  I naively assumed that once they know what riches are contained in the thousands of journals the University subscribes to they would spend every spare moment searching and reading. Nope.  It seems that we teach this skill and the student promptly ignore it.  Perhaps this is because the library has a pretty good search engine itself that can retrieve relevant papers without the need to use database like Medline and Cinahl. The problem however it that this search facility is not as good as the specialist databases and therefore the students never discover how much further they could go with a well designed search.

Despite a number of efforts to teach the students the skills and the value of literature searching they arrive at the dissertation module at the beginning of year 3 virginal.  We have just spent a couple of weeks with them helping them remember and practice their search skills.  Many have found the process confusing and frustrating.  I found myself musing that my own skills have developed over many years but I am still learning new techniques and how to get the best out of each database.  So I don’t expect a novice to grasp it straight away but I think to myself that if he or she had started using the databases in year 1 by year 3 they would be pretty self-sufficient and find the search component of their dissertation easy.  A colleague hit the nail on the head I think when he said that he felt people only ever use a skill when they need to.  We have the same argument about teaching advanced clinical skills like phlebotomy and cannulation.  Should we teach this to student nurses who won’t get to practice those skills on placement and as a consequence will lose their competence?  If we don’t require the students to search – if they can get by without it – why should they use it?

There are some top tips that have begun to emerge as the students ask questions about searching.

  1. Search one database at a time and check the box that says ‘suggest search terms’.  This will allow the database to provide you with the term that best encapsulates what you want to find.
  2. Explode a search if you want the database to provide you with results that contain your major concept plus all the related concepts.  You can click on the hyperlink contained in the search term to show you what those other terms are.
  3. Select major concept if you only want results where your term is the main focus of the paper.  I don’t use this strategy very often because it creates a risk that you will miss some terms.
  4. Search for one term at a time.  If you use a search string (e.g. pain AND nurs* AND opioid) you won’t get MeSH terms or subject headings or suggestions.
  5. Think about what terms you don’t need to include in your search.  An excellent example of this occurred today in a search relating to the experiences of parents who were caring for a child at the end of life at home. Creating a search that included a number of terms for ‘child’ was not as good as leaving that term out.  Child is implicit when you search for parent and this seemed to yield a better set of data.
  6. Consider whether you want EVERYTHING that is published or a SAMPLE. In some qualitative review methods you don’t actually want everything, you just want a diverse sample of what is out there.  In the undergraduate review this is not a good strategy because you have to justify your rationale and this rationale is difficult to justify.
  7. Record everything as you go along.  This means saving your searches so that you can edit them and re-run them as often as you like.  Saving in OVID and EBSCO allows you to run searches on multiple databases without having to recreate them each time.
  8. Create your methods section as you undertake your searches.
  9. Use the inclusion and exclusion criteria to define your search and provide the scope for your question.
  10. Export the results of all searches, after applying the relevant limits, to a database like RefWorks or EndNote.  This will allow you to de-duplicate and work towards your final set of papers gradually and systematically.

Publishing as a student nurse

We design our Undergraduate dissertation as a publishable literature review.  This is a strategy that has been used in quite a few postgraduate assessments and helps the student to prepare their work for publication.  It is very important to me that nurses know that they have something important to say, and to share.  Too many lack the confidence that seems to be a given in other health professional students.

This week congratulations are due to two students.  One undertook her elective placement at the Nursing Times and has subsequently had published an interview that she conducted.



The second is Rachel Cater, whose dissertation submitted in 2017 has just been published in the Journal of Clinical Nursing.  Thanks are due to Professor Julie Taylor (@bulawayojulie) who supervised and supported Rachel.


I’ve got at least 2 of these joint publications ready to submit now.  We are making progress since the days when it was almost unheard of for a student to publish, but my clinical practice tells me that many qualified nurses are just as under-confident in their writing skills.  A very quick glance through one journal’s current issue identified that most of the papers were authored by academics, relatively few by clinicians and only one by a student nurse.

There is a lot of literature out there about the benefits to the individual, the organisation and patients for publishing.  There is also evidence that editors are not always impressed by the quality of student submissions.  We recommend that you write your dissertation up for publication with the support of your supervisor.  It does take quite a lot of work to get from dissertation to submission-ready, and every submission will require revision once it as been peer-reviewed.  But it is worth it 🙂