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Evidence - based medicine

Evidence - based medicine. Course: Research in Biomedicine and Health III Seminar 3 : Looking for evidence. What is EBM in practice ?. EBM steps Step 1: Formulating questions that can be answered Step 2: Finding best evidence Step 3: Quick critical assessment of the evidence

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Evidence - based medicine

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  1. Evidence-based medicine Course: Research in Biomedicine and Health III Seminar 3: Looking for evidence

  2. What is EBM inpractice? • EBM steps • Step 1: Formulating questions that can be answered • Step 2: Finding best evidence • Step 3: Quick critical assessment of the evidence • Step 4: Applying evidence • Step 5: Assessing effectiveness and efficiency of the process

  3. How to ask a clinical question? “PICOT” model: Patient (For which patient, population or problem you need information?) Intervention/indicator (What is the intervention you are studying?) Comparison/control (Which is the alternative treatment?) Outcome (What is the effect of the intervention?) • Type of study • (Which is the optimal study design ?) What is the study design? What is the comparison? Who is treated? What is given as a treatment? What outcome is of interest to us?

  4. Aimofsteps 1. i 2. : find “pearls”

  5. Sources of evidence • Journals (“Online evidence-based journals of secondary publications”) • Databases(“Evidence-based databases”) • Clinical guidelines (“Online evidence-based clinical practice guidelines”)

  6. Online EBM journals: Restricted access journals: • ACP Journal Club; http://www.acpjc.org Availabe via OVID (CARNet) - Evidence-Based Medicine; http://ebm.bmjjournals.com - Evidence-Based Mental Health; http://ebmh.bmjjournals.com - Evidence-based Obstetrics and Gynecology; http://www.harcourt-international.com/journals/ebog Free access journal: - Bandolier; http://www.jr2.ox.ac.uk/bandolier/

  7. EBM databases • The Cochrane Library (http://www.cochrane.org) • The DARE • The Cochrane Controlled Trials Register (CENTRAL)

  8. Other EBM databases(free access): • PubMed Clinical Queries (http://www.ncbi.nlm.nih.gov/entrez/query/static/clinical.shtml) • SUMSearch (http://sumsearch.uthscsa.edu/) • TRIP Database (http://www.tripdatabase.com )

  9. Keyword: “cough”

  10. Keyword: “persistentcough” – PubMedClinicalQueries

  11. OnlineEBM guidelines • The National Guideline Clearinghouse (NGC) (http://www.guideline.gov ) • Primary Care Clinical Practice Guidelines (http://medicine.ucsf.edu/resources/guidelines/index.html).

  12. I intervention C Comparison (not always) Be precise! P Patient, problem T Type of study O Outcome Kew words for database search

  13. Searchstrategy Recommended procedure: • Determine key words and see if you can find them in MeSH-u and chooserelevant MeSH term for database search. • Decide which question type you are looking for, depending on the purpose (therapy, diagnosis, prognosis etc. ). • Determine study design that is best for your question (RCT, case-control, cohort) (try to find metaanalysis or systematic review) • Choose the database and search it according to relevant key words.

  14. Settingupsearchstrategy • Carefully formulate the question • Break the question into individual concepts • Break each concept into related terms and synonims • Decide on the grammatical form of each term within a concept • Connect all terms within the same concept with OR operator • Combine different concepts with AND operator

  15. Searchstrategies for clinicalquestions • Based on PICO(T) model • It is not necessary to search each aspect of the clinical question using the PICO(T) model – this would narrow the search too much. • Search strategy usually has three elements: • Terms (MeSH and free key words) which describe health care condition (population, problem) • Terms describing the intervention • Terms describing study designs (not used in some databases which archive only studies of specific study design, like CENTRAL of the Cochrane collaboration)

  16. Searchsensitivityandprecision • Sensitivity • Aim of such strategy is to find as many papers, even those that are not very focused onthe topic. • It is used when we estimate that the available literature is not large or when a large number of relevant studies is needed. • Precision • Strategy aims to find most important papers. • It is defined as the ratio between the number of identified relevant studies and number of retrieved studies.

  17. Operators • Operators are words or signs that have specific function whithin the syntax unit during search. • They determine the relationship between the key words within syntactic units and the whole search strategy. • The make search more precise. • Most common are Boolean operators.

  18. Booleanoperators • AND • OR • NOT • George Boole (1815 – 1864) – English mathematician, developed algebraic system consisting of only two possible states.

  19. Example FIRST CONCEPT • 1st keyword about patient/disease • 2nd keyword about patient/disease • 1 OR 2 • 1st keyword about intervention • 2nd keyword about intervention • 4 OR 5 • 1st keyword about study design • 2nd keyword about study design • 7 OR 8 • 3 AND 6 AND 9 SECOND CONCEPT THIRD CONCEPT

  20. Nesting • Nesting is searching for groups of keywords in a single search • Grouping is achieved by brackets • Example: • (1 OR 2) AND (3 OR 4 OR 5 OR 6) AND (7 OR 8) FIRST CONCEPT SECOND CONCEPT THIRD CONCEPT

  21. Controlledvocabularyoffreelychosenkeywords? • Good search strategy should include both if the database uses a controlled vocabulary such as MeSH. • Terms should be chosen for each concept. • Terms can be chosen according to a relevant article, which is indexed according to MeSH terms. • MeSH Database (PubMed) can also be used to identify relevant terms.

  22. MeSHstructure

  23. ExampleofusingMeSHandfreekeywords • Osteoporosis, Postmenopausal/ • osteoporo$.ti,ab. • Bone Density/ • (bone adj5 (densit$ OR loss OR mass)).ti,ab. • BMD.ti,ab. • Fractures, Bone/ • fracture$.ti,ab. • OR/1-7

  24. ExampleofullstrategySampson M, McGowan J, Lefebvre C, Moher D, Grimshaw J.PRESS: Peerreviewofelectronicsearchstrategies, 2008. MEDLINE (OVID) 1. search$.tw. 2. exp "information storage and retrieval"/ or Medical Informatics/ 3. Data Compression/ 4. 2 not 3 5. or/1,4 6. quality control/ or Evaluation Studies/ or "reproducibility of results"/ 7. (quality adj2 assess$).tw. 8. or/6-7 9. (quality or evaluat$).tw. 10. (precision or recall or sensitivity or relevance or specificity).tw. 11. (performance adj2 (measur$ or indicat$ or assess$)).tw. 12. "Sensitivity and Specificity"/ 13. or/10-12 14. (error$ or mistake$ or failure$ or inaccura$ or misspell$).tw.

  25. 15. (MeSH or (subject adj2 heading$) or (controlled adj2 vocabulary) or redundan$ or explod$ or explos$ or spell$ or Medline).tw. 16. truncat$.tw. 17. (truncat$ adj6 (protein$ or gene$)).mp. 18. 16 not 17 19. exp Documentation/ 20. exp Molecular Sequence Data/ 21. 19 not 20 22. or/15,18,21 23. EVIDENCE-BASED MEDICINE/ 24. META-ANALYSIS/ 25. Review.pt. 26. "Review Literature"/ 27. or/23-26 28. "INFORMATION STORAGE AND RETRIEVAL"/st [Standards] 29. and/27-28 30. and/5,8,13 31. and/5,13-14 32. and/9,13,22 33. or/29-32 34. "cochrane database of systematic reviews".jn. 35. 33 not 34 36. limit 35 to yr=1980 - 2005

  26. ACP Journal Club / Cochrane Database of Systematic Reviews Pubmed (MEDLINE) “AND” meta-analysis Metaanalysis ACP Journal Club / Cochrane Database of Systematic Reviews Pubmed (MEDLINE) Clinical Queries (Systematic Reviews) Systematic review ACP Journal Club / Cochrane Central Register of Controlled Trials Pubmed (MEDLINE) Clinical Queries (Therapy) RCT PubMed (MEDLINE) “AND” cohort study Cohort study PubMed (MEDLINE) “AND” case control study Case-control study Case series/case reports PubMed (MEDLINE) “AND” case report

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