Searching the literature by xiaohuicaicai


									                       SEARCHING THE LITERATURE
     “Seventy-five trials and eleven systematic reviews a day: how will we ever keep up?”
                        Bastian H, Glasziou P, Chalmers I. PLoS Med 2010

1. Background questions are general questions, usually of etiology,
   pathophysiology and prognosis of disease. Example: “What causes carpal
   tunnel syndrome?”, “Why is there no edema in patients with SIADH?”
2. Foreground questions are more specific questions, usually of diagnosis,
   harm and therapy but also of etiology or prognosis. Example: “Does use of
   B-complex vitamins reduce pain and numbness in patients with carpal
   tunnel syndrome?”
3. Defining the Patient, Intervention in question and possible Outcomes may
   help in formulating a foreground clinical question: “Does use of B-complex
   vitamins (intervention) reduce pain and numbness (outcomes) in patients
   with carpal tunnel syndrome?”
4. When performing literature search for a foreground question it may be
   helpful to consider whether you anticipate to find few or numerous studies.
   If multiple studies are expected it will be more efficient to search for a
   systematic review (for one intervention) or evidence synthesis (for multiple
   interventions). If few studies are expected on the topic, one may have to
   search for the original studies in MEDLINE, primary journals or abstracts of
   those studies in secondary journals or pre-appraised sources.

                              Foreground                              Background
                               question                                question

          Many studies                     Few studies likely       Narrative reviews
         likely available                     available
                                                                   (Textbooks, Journals,

      Look for systematic             Look for original studies:
    reviews or synthesis of
       Clinical Evidence              1. Appraised: ACP Journal
                                         Club, Journal Watch,
           UpToDate                    Essential Evidence plus
        TRIP database
        PIER modules                   2. Unfiltered: MEDLINE,
      Cochrane database                    Primary Journals

 BMJ Clinical Evidence, ACP PIER modules and UpToDate provide
  summaries of evidence categorized by disease/disorder. This allows one to
  search for the evidence on multiple interventions (screening, diagnosis,
  therapy etc) regarding the same disorder. The uptake of the most recent
  studies by these resources may not be immediate, so searching for
  individual trials may still be necessary.
 Clinical Evidence categorizes the interventions as beneficial, likely to be
  beneficial, trade off between benefits and harms, unlikely to be beneficial,
  likely to be ineffective or harmful and unknown effectiveness. This is based
  on their assesment of available evidence.
 UpToDate uses the GRADE system to rate the quality of evidence and
  provide recommendations:

                Recommendation                               Quality of Evidence
        Grade 1: Strong (most patients will      A: High-quality (multiple high quality
                      benefit)                          RCTs or systematic reviews)
        Grade 2: Weak (balance of benefits            B: Moderate-quality (RCTs with
            and harm close or uncertain)                   limitations or high quality
                                                             observational studies)
                                                       C: Low-quality (poor quality
                                                       observational data, expert opinion
                                                           or RCTs with major flaws)

 The Cochrane database provides among others, systematic reviews
  prepared by the Cochrane Collaboration (Cochrane Database of Systematic
  Reviews-CDSR), systematic reviews prepared by others (Database of
  Abstracts of Reviews of Effects-DARE) and a large database of RCTs
  (Cochrane Central Register of Controlled Trials-CENTRAL).

 TRIP database allows search for all levels of evidence (synopses, systematic
  reviews, pre-appraised and original studies). It also provides a filter to
  enable search for only high quality evidence.

 ACP Journal Club provides structured abstracts of original studies along
  with expert commentary.

 MEDLINE is a vast but relatively unfiltered source of original studies but
  also of systematic reviews, practice guidelines etc.

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