How to Read a Paper: The Basics of Evidence-Based Medicine (7 page)

All of these sources may be considered as small databases of select studies, which may be searched by keyword. Other selected journal article services, such as Evidence Updates, provide abstracts plus an indication of level of interest each article might hold for particular disciplines.

DARE
was mentioned as a pre-appraised source for systematic reviews other than Cochrane Reviews, in that it provides an augmented abstract and a brief critical appraisal for most systematic reviews in its database.

Another source that is considered pre-appraised, although it contains no appraisals, is the
Central Register of Controlled Trials
, also part of the Cochrane Library. ‘Central’ is a bibliography of studies included in Cochrane Reviews, as well as in new studies on similar topics, maintained by the various Cochrane Review Groups. DARE, Central, the Cochrane Database of Systematic Reviews, the HTA database and the NHS Economic Evaluation Database—which also includes critically appraised summaries of studies—may all be searched simultaneously in the Cochrane Library.

Specialised resources

Specialised information sources, organised (as the name implies) to assist the specialist doctor in a particular field, are often also useful for generalists, specialist nurses and primary care clinicians. Most professional associations maintain excellent websites with practice guidelines, journal links and other useful information resources; most require membership in the association to access educational and practice materials. Three notable examples that are available for a fee are Global Infectious Diseases and Epidemiology Network (GIDEON), Psychiatry Online and CardioSource.

• GIDEON
  (
  Global Infectious Diseases and Epidemiology Network
  ,
  http://www.gideononline.com
  /) is an evidence-based programme that assists with diagnosis and treatment of communicable diseases. In addition, GIDEON tracks incidence and prevalence of diseases worldwide and includes the spectrum covered by antibiotic agents.
  
• Psychiatry Online
  (
  http://www.psychiatryonline.com
  /) is a compendium of core textbooks (including Diagnostic and Statistical Manual of Mental Disorders fifth edition (DSM V)), psychiatry journals and practice guidelines of the American Psychiatric Association, produced by the American Psychiatric Press.
  
• CardioSource
  (
  http://www.cardiosource.com
  ) is produced by the American College of Cardiology. It includes guidelines, journal and textbook links, ‘clinical collections’ of articles and educational materials on topics such as cholesterol management and atrial fibrillation, and an excellent clinical trials registry for all trials relating to cardiovascular disease, whether ongoing or completed.
  

These three are only examples. Whatever your specialty (or specialist topic), there will usually be a similar resource maintained by a professional society. Ask a librarian or clinical informaticist to help you find the relevant one!

Primary studies—tackling the jungle

Whether through habit or through lack of familiarity with all the useful synthesised, summarised or pre-appraised sources described earlier, most health practitioners still prefer a basic search of Medline/PubMed to answer their clinical information needs. Some simply prefer to assess the primary literature for themselves, without thumbnail critical appraisals or incorporation into larger disease management chapters. I still advise you to go for the secondary sources described in sections ‘Levels upon levels of evidence’, ‘Synthesised sources: systems, summaries and syntheses’ and ‘Pre-appraised sources: synopses of systematic reviews and primary studies’, but if you would like to go direct to the primary studies, this section is for you.

Primary sources can be found in a variety of ways. You could look at the reference lists and hyperlinks from the secondary sources described. You could identify them from journals—for example, via RSS feeds, table-of-contents services or more focused topical information services. And you could search databases such as PubMed/Medline, EMBASE, PASCAL, Cochrane Library, CINAHL (Cumulated Index of Nursing and Allied Health Literature), Biosis Previews, Web of Science, Scopus or Google or Google Scholar. I consider these one by one here.

PubMed is the most frequently accessed Internet resource for most physicians and health professionals worldwide, probably because it is free and well-known. Most people opt for the basic PubMed search, using two or three search text words at best—and characteristically turning up hundreds or thousands of references, of which they look at only the first couple of screens. This is certainly not the most efficient way to search, but it is the reality of how most people
do
search [7]. Interestingly, when just one or two more search terms are added, the efficiency of a basic PubMed search improves substantially [7].

Simple tools that are part of the Medline search engine can be used to help focus a search and produce better results for a basic search, but they are rarely used by medical students or doctors. One such tool is the ‘
limit
’ function, allowing restrictions to such generic topics as gender, age group or study design; to language or to core clinical journals. The advanced search function on PubMed incorporates these limits into a single search page. Next time you are on the PubMed website with some time to spare, play with these tools and see how easily they can sharpen your search.

‘
Clinical queries
’, an option provided in the left-hand panel of the basic PubMed screen or at the bottom of the advanced search screen, superimposes on the search a filter based on optimum study designs for best evidence, depending on the domain of the question and the degree to which one wishes to focus the question. For example, if you were searching for a therapy study for hypercholesterolaemia, the clinical query for therapy/narrow and specific would be rendered as ‘(hypercholesterolaemia) AND (randomised controlled trial [Publication Type] OR (randomised [Title/Abstract] AND controlled [Title/Abstract] AND trial [Title/Abstract]))’. In this instance, the search might need further limits or perhaps the addition of a second term, such as a specific drug, because the result is over 2000 postings.

Citation chaining
(or, to use its alternative term,
citation tracking
) provides another means of following a topic. Let's say that, following your interest in hypercholesterolaemia, you wish to follow up a classic primary research study, the West of Scotland Coronary Prevention Study, originally published in the 1990s [8]. In your PubMed search, you found a study in the New England Journal of Medicine in 2007 that described a 20-year follow-up [9], but you now wonder if there has been anything further. The databases Web of Science, comprising Science Citation Index, Social Sciences Citation Index and the Arts and Humanities Citation Index online, provide a cited reference search feature. Entering the author's name (in this case I. Ford) and the year of publication (2007), we can trace the specific article, and find that several dozen articles published since have cited it in their reference lists. Citation searching can give a crude indication of the relative importance of a study, based on the number of times it has been cited (bearing in mind that one sometimes cites a paper when emphasising how bad it is!). A very simple (but somewhat less accurate) way of citation chaining is to use Google Scholar: simply put the article's title into this search engine and when you have found it, select ‘citations’.

Google Scholar, a very broad-based web browser, is increasingly popular and extremely handy, accessible as it is from the Google toolbar. For an obscure topic, Google Scholar can be an excellent resource on which to fall back, as it will identify papers that are listed on PubMed as well as those that aren't. Unfortunately, there are no quality filters (such as clinical queries), no limits (such as gender or age), so a search on a widely researched topic will tend to turn up a long list of hits that you have no alternative but to wade through.

One-stop shopping: federated search engines

Perhaps the simplest and most efficient answer for most clinicians searching for information for patient care is a federated search engine such as TRIP,
http://www.tripdatabase.com
/, which searches multiple resources simultaneously and has the advantage of being free.

TRIP
has a truly primitive search engine, but it searches synthesised sources (systematic reviews including Cochrane Reviews), summarised sources (including practice guidelines from North America, Europe, Australia/New Zealand and elsewhere, as well as electronic textbooks) and pre-appraised sources (such as the journals
Evidence-Based Medicine
and
Evidence-Based Mental Health
), as well as searching all clinical query domains in PubMed simultaneously. Moreover, searches can be limited by discipline, such as Paediatrics or Surgery, helping both to focus a search and eliminate clearly irrelevant results and acknowledging the tendency of medical specialists to (rightly or wrongly) prefer the literature in their own journals. Given that most clinicians favour very simple searches, a TRIP search may well get you the maximum bang for your buck.

Asking for help and asking around

If a librarian fractured her wrist, she would have no hesitation in seeking out a physician. Similarly, a healthcare professional doesn't need to cope with the literature alone. Health librarians are readily available in universities, hospitals, government departments and agencies and professional societies. They know the databases available, they know the complexities of searching, they know the literature (even complex government documents and obscure data sets), and they usually know just enough about the topic to have an idea of what you are looking for and levels of evidence that are likely to be found. When one librarian can't find an answer, there are colleagues with whom he can and will consult, locally, nationally and internationally. Librarians of the 21st century are exceptionally well networked!

Asking people you know yourself or know about has its advantages. Experts in the field are often aware of unpublished research or reports commissioned by government or other agencies—notoriously hard-to-find ‘grey’ or ‘fugitive’ literature that is not indexed in any source. An international organised information-sharing organisation CHAIN (Contact, Help, Advice and Information Network,
http://chain.ulcc.ac.uk/chain
) provides a useful online network for people working in health and social care who wish to share information. CHAIN can be joined for free and once a member, you can pitch in a question and target it to a designated group of specialists.

In a field as overwhelming and complex as health information, asking colleagues and people you trust has always been a preferred source for information. In the early days of evidence-based medicine (EBM), asking around was seen as unsystematic and ‘biased’. It remains true that asking around is insufficient for a search for evidence, but in the light of the ability of experts to locate obscure literature, can any search really be considered complete without it?

Online tutorials for effective searching

Many universities and other educational institutions now provide self-study tutorials, which you can access via computer—either on an intranet (for members of the university only) or the Internet (accessible to everyone). Here are some I found when revising this chapter for the fifth edition. Note that as with all Internet-based sources, some sites will move or close down, so I apologise in advance if you find a dead link:

• ‘
  Finding the Evidence
  ’ from the University of Oxford's Centre for Evidence-Based Medicine. Some brief advice on searching key databases but relatively little in the way of teaching you how to do it. Perhaps best for those who have already been on a course and want to refresh their memory.
  http://www.cebm.net/index.aspx?o=1038
  .
  
• ‘
  PubMed—Searching Medical Literature
  ’ from the Library at Georgia State University. As the title implies, this is limited to PubMed but offers some advanced tricks such as how to customise the PubMed interface to suit your personal needs.
  http://research.library.gsu.edu/pubmed
  .
  
• ‘
  PubMed Tutorial
  ’ from PubMed itself. Offers an overview of what PubMed does and doesn't do, as well as some exercises to get used to it.
  http://www.nlm.nih.gov/bsd/disted/pubmedtutorial
  /.
  

There are many other similar tutorials accessible free on the Internet, but few of them cover much beyond searching for primary studies and systematic reviews in PubMed and the Cochrane Library. I hope that by the time the next edition of this book is due, someone will have redressed this bias and developed tutorials on how to access the full range of summaries, syntheses and pre-appraised sources I described in earlier sections.

References

1
Davies K. The information seeking behaviour of doctors: a review of the evidence.
Health Information & Libraries Journal
2007;
24
(2):78–94.

2
Fourie I. Learning from research on the information behaviour of healthcare professionals: a review of the literature 2004–2008 with a focus on emotion.
Health Information & Libraries Journal
2009;
26
(3):171–86.