The shape of clinical literature
The mass of published literature now far exceeds our ability to cope with it as individuals; the evidence for practice is out there but in blinding volume and in a bewildering array of formats and platforms. Experienced clinicians in the past have tended to choose one or two principal sources of information, often old friends such as PubMed, a general journal such as BMJ or the New England Journal of Medicine, plus two or three journals in their specialty – say, Urology, BJU International or European Urology – and stick with them. This is no longer sufficient to allow a practitioner to keep up with new relevant and applicable clinical research. However, in a very positive turn of events over the past decade, the geometrically growing mass of published clinical research has brought with it the development of resources to summarize and synthesize this new knowledge and present it in methodologically sound and extremely accessible formats. Armed with these resources and a few relatively simple techniques, it is indeed possible to find evidence for practice quickly and efficiently.
The literature of evidence for practice follows a hierarchical structure based on the degree of processing and appraisal applied to the primary research literature [1] (see Box 1.1). Summaries and syntheses of the evidence, including practice guidelines, are at the top, followed by preappraised synopses, with primary studies at the base. Typically, the search for evidence for clinical practice starts at the top, in the summaries and syntheses, dropping down to synopses and systematic reviews. If a satisfactory result has not been found or if the searcher wishes for more recent evidence, primary research studies are the final resource. Unfortunately, the primary literature is massive: a simple PubMed search for prostate cancer at the time of this writing (November 2015) turned up over 131 000 references. Using Clinical Queries, as we recommend in PubMed to filter in the research literature, in this case for therapy studies, reduced the number to 3450 randomized controlled trials (RCTs) and 3271 systematic reviews. These very daunting numbers persuade clinicians of the value of starting at the top of the evidence pyramid for general questions. For more specific questions, search results will usually be less alarming.
BOX 1.1 A hierarchy of resources.
- Summaries, syntheses and guidelines
- 1.1 Point‐of‐care summaries (e.g. DynaMed, UpToDate)
- 1.2 Practice guidelines (e.g. NICE, International Guidelines Clearinghouse)
- 1.3 Evidence‐based textbooks (e.g. Campbell–Walsh Urology and other textbooks available via Clinical Key, Access Medicine, and Books@Ovid)
- Preappraised research
- 2.1 Synopses of systematic reviews (e.g. DARE [Database of Abstracts of Reviews of Effects], ACP Journal Club)
- 2.2 Systematic reviews (e.g. Cochrane Reviews)
- 2.3 Synopses of primary studies (e.g. ACP Journal Club, Evidence‐Based Medicine, McMasterPLUS)
- Primary studies
- 3.1 Filtered (e.g. Clinical Queries in MEDLINE/PubMed)
- 3.2 Unfiltered (e.g. PubMed, EMBASE, BIOSIS, Web of Science)
Some “federated searches” are available that are structured to search simultaneously through all three categories of evidence and present the results according to evidence levels. TRIP (Turning Research Into Practice, https://www.tripdatabase.com) is one such search engine, freely accessible worldwide (registration is free and provides more unrestricted access to content than unregistered use).
The approach for finding evidence for practice is exactly the opposite of that for conducting a literature review at the beginning of a research project. In the case of the literature review, one conducts a thorough search of all appropriate bibliographic databases: MEDLINE (whether via PubMed or some other search interface), EMBASE, Web of Science, Scopus, Biosis Previews, plus resources such as the Cochrane Library, to ensure one has not missed an important controlled trial or systematic review, and databases listing clinical trials in progress, to ensure that all relevant studies have been found. If possible, one consults a research librarian to be sure that no stone has been left unturned.
However, to find evidence to apply to clinical problems, the search begins with synthesized resources, progresses through selected, preappraised resources, and moves into bibliographic databases of primary studies only if no satisfactory answer has been found in the first two resource classes. With a literature review, the search is exhaustive. With the search for clinical evidence, it is acceptable to stop when a good answer has been found.
Some of the resources described in this chapter are free; most are broadly available to those affiliated with medical societies or institutions or are available by individual subscription. New synthesized resources, point‐of‐care resources in particular, are continually emerging as established resources evolve. How does one choose among these resources? Availability and affordability are two obvious factors, but consider also how well a resource covers your discipline, how current the resource is, and how quickly it updates and includes new evidence, whether its inclusion practices are transparent and its authorship explicitly stated, whether the evidence is assessed for quality and citations are provided for all summaries and recommendations, and whether there are numerical estimates of effect provided within the summaries. Ease of use is vitally important. Some recent studies have compared point‐of‐care resources for currency, inclusion of new evidence, and ethical factors [2–4]. Consideration of all of these factors will assist clinicians to become enlightened consumers of complex information resources.
A case to consider
Mr. W, 63 years old and otherwise fit and healthy, has been referred to you with symptoms of benign prostatic hyperplasia (BPH) (frequency, nocturia, and slow flow). Digital rectal examination reveals an enlarged prostate gland, about 45 g, with no nodules. His postvoid is approximately 100 mL and he reports three documented urinary tract infections over the course of the last year. His serum creatinine and prostate‐specific antigen (PSA) levels are normal.
He has been advised by his family physician that he may require surgery to resolve his condition. He is apprehensive about this and asks if there are medical interventions for the BPH that could be tried first. He has searched the ...