Evidence-Based Medicine


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One of the sessions on the learning centre on the World Congress of Internal Medicine Granada 2004

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Evidence-Based Medicine

  1. 1. Evidence Based Medicine:Evaluating and translating evidence into clinical practice Francisco Javier Rodríguez-Vera Department of Internal Medicine Hospital do Barlavento Algarvio Portimão Portugal. EU
  2. 2. Evidence Based Medicine: What itis?Main Entry: 1ev·i·dencePronunciation: e-v&-d&n(t)s, -v&-"den(t)sFunction: noun1 a : an outward sign : INDICATION b : something that furnishes proof :TESTIMONY; specifically : something legally submitted to a tribunal toascertain the truth of a matter2 : one who bears witness; especially : one who voluntarily confesses a crimeand testifies for the prosecution against his accomplices
  3. 3. “Is the process of systematically reviewing,appraising and using clinical research findings to aidthe delivery of optimum clinical care to patients”Rosenberg W, Donald A. Evidence-based Medicine: an approach to clinicalproblem solving. BMJ 1995; 310 (6987):1122-1126 Consists in decision making according the state of the art of the medical knowledge
  4. 4. Evidence Based Medicine: Why?
  5. 5. Evidence Based Medicine: Why?
  6. 6. Is a tool for the efficient management of the knowledge
  7. 7. Evidence Based Medicine
  8. 8. Where is evidence?
  9. 9. Reasoning and intuition Published evidenceColleagues Personal experience Bottom drawer
  10. 10. Where is evidence? Personal experience Reasoning and intuition Colleagues Bottom drawer (pieces of paper in the office) Published evidence
  11. 11. Levels of evidenceI. Strong evidence from at least one systematic review of multiple well designed randomised controlled trials.II. Strong evidence from at least one properly designed randomised controlled trial of appropriate size.III. Evidence from well designed trials such as non-randomised trials, cohort studies, time series matched case- controlled studies.IV. Evidence from well-designed non-experimental studies from more than one centre or research group.V. Opinions of respected authorities, based on clinical evidence, descriptive studies or reports of expert committees.
  12. 12. - systematic review + randomised controlled trialNumber of Level of studies evidence non-randomised trials, cohort - studies, time series matched+ case-controlled studies. non-experimental studies Opinions
  13. 13. How to do Evidence Based Medicine. Steps. 1. Elaboration of a clinical question 2. Searching the information 3. Critical appraise. 4. Application to our case
  14. 14. How to make a clinical question.Questions in Evidence Based Medicine will have to bemade in clear and well defined terms:oPerson or population in questionoIntervention givenoComparison (if appropriate)oOutcomes consideredThe best question is that which can be answered with Yes or No
  15. 15. Patient or Problem Intervention Comparison Intervention OutcomeDescription of the patient or the Could Relevant most often when looking Clinical outcome of interest totarget disorder of interest include: at therapy questions you and your patient •Exposure •Diagnostic test •Prognostic factor •Therapy •Patient perception etc.
  16. 16. QuestionsTherapyPrognosisDiagnosisHarm/Etiology
  17. 17. TherapyYou admit a 65 year old man with a stroke. On examinationyou find that he has mild weakness of the right arm andright leg and bilateral carotid bruits. You send the patientfor carotid doppler ultrasonography and subsequentlyreceive the report that he has moderate stenosis (50-69%by NASCET criteria) of the ipsilateral carotid artery. Youwant to now if aspirin will be indicated in this patient.
  18. 18. Can ASA decrease the risk of stroke?
  19. 19. Patient or Problem Intervention Comparison Intervention Outcome65 year old man with a stroke and moderate carotid stenosis ASA Placebo Stroke
  20. 20. In a 65 year old man with a stroke and moderatecarotid stenosis, can ASA decrease the risk of anotherstroke compared with no treatment?
  21. 21. PrognosisYou see a 70 year old man in your outpatient clinic 3 monthsafter he was discharged from your service with an ischemicstroke. He is in sinus rhythm, has mild residual left-sidedweakness but is otherwise well. His only medication is ASAand he has no allergies. He recently saw an article on theBMJ website describing the risk of seizure after a stroke andis concerned that this will happen to him.
  22. 22. Patient or Problem 70 year old manIntervention StrokeComparison InterventionOutcome SeizureQuestion In a 70 year old man does a history of stroke increase his risk for seizure?In a 70 year old man does a history of stroke increase hisrisk for seizure?
  23. 23. DiagnosisYou admit a 75 year old woman with community-acquiredpneumonia. She responds nicely to appropriate antibioticsbut her hemoglobin remains at 10 g/dl with an MCV of 80.Her peripheral blood smear shows hypochromia, she isotherwise well and is on no incriminating medications. Youcontact her family physician and find out that her Hgb was10.5 g/dl 6 months ago. She has never been investigatedfor anaemia. A ferritin has been ordered and comes backat 10 mmol/l. You admit to yourself that youre unsurehow to interpret a ferritin result and arent sure howprecise and accurate it is.
  24. 24. Patient or Problem Elderly woman with anaemiaIntervention FerritinOutcome Iron deficiency anaemiaQuestion In an elderly woman with hypochromic, microcytic anaemia, can a low ferritin diagnose iron deficiency anaemia?In an elderly woman with hypochromic, microcytic anaemia,can a low ferritin diagnose iron deficiency anaemia?
  25. 25. Harm/EtiologyYou see a 50 year old man who asks for a repeatprescription of sotalol which he has been taking forextrasystoles for several years. He has a remote historyof an MI. You havent seen him previously and areconcerned about the proarrhythmic properties of sotalolgiven what is known about other antiarrhythmics.
  26. 26. Patient or Problem Man with extrasystolesIntervention SotalolCompar Intervention PlaceboOutcome DeathQuestion In a man with extrasystoles and a remote history of MI, does treatment with sotalol increase his risk of death? In a man with extrasystoles and a remote history of MI, does treatment with sotalol increase his risk of death?
  27. 27. How to do Evidence Based Medicine. Steps. 1. Elaboration of a clinical question 2. Searching the information 3. Critical appraise. 4. Application to our case
  28. 28. Searching the information• Background Resources: • Give overview of a topic; print textbooks, electronic textbooks, narrative reviews in journals 1. Harrison’s Online 2. Scientific American Medicine Online 3. MD Consult 4. Medline (for narrative review articles) a. Ovid b. PubMed
  29. 29. •Foreground Resources: (reports of original research orabstracts, summaries, syntheses of primary research) • Secondary Sources-abstracts, summaries and syntheses of original research 1. Cochrane Database of Systematic Reviews- systematic review of a topic •2. ACP Journal Club- review and commentary of an article •3. Clinical Evidence -  summarizes evidence available for common clinical questions-includes Cochrane and ACP Journal Club report (direct) 4. Practice Guidelines
  30. 30. • Primary Sources-reports of original research1. OVID Medline2. PubMed Medline
  31. 31. It indexes nearly 9 million records representingarticles from more than 3,600 biomedicaljournals published world-wide. http://www.pubmed.org includes the full text of the regularly updated systematic reviews of the effects of healthcare interventions (therapy) prepared by The Cochrane Collaboration. http://www.cochrane.org
  32. 32. PubMedCreated for the National Library of MedicineThree forms of presentation: Full text (links to the journal) Abstracts (papers and original articles) Title and Authors (Letters to editor)
  33. 33. PubMed. Advantages and inconvenients It accumulates the most Publications not relevant journals included: grey literature Free Requires learning Updated Full text not avalaible in all pubblications
  34. 34. PubMed: an example of a search We want to know what´s the state of the art of the treatment of a myocardial infarction"Myocardial Infarction/therapy"[MeSH]: 37326 arts Limits: arts with abstract: 20310 arts Add limit Clinical Meta-analysis: 167 arts change limit: clinical practise guideline: 23 artsWritten in English and published in the last year: 4 arts
  35. 35. Evidence Based medicine: After the efficient searchDepending the subject a search may give from 5to 500 entries.Reading of abstracts and elimination of articles“After reading abstracts the search was limitedto…”Reading of articles in full text “After the reading in full text, the searchwas limited to….articles”
  36. 36. The problem of obtaining articles How would i get a full text article?Official site of the journalAccumulatorsAsking the author for a copy of the articleSites with passwords to fulltext
  37. 37. Some articles are avalaible full text for free
  38. 38. http://intl.highwire.org/ http://ebro3.unizar.es:8080/rev/default.html
  39. 39. “Dear Dr …I´m researching on…., and in a search in PubMed Ifound the abstract of your study published in…, which Ifound extremely interesting. I would be pleased if youcould provide my with a separata of your article.Sincerely yours…”
  40. 40. Now, we have articles that may give an answer to our clinical question Are these articles reliable?
  41. 41. I. Level of evidence provided by the articleII.Possibility of bias (internal coherence) of the article
  42. 42. Levels of evidence- systematic review + randomised controlled trialNumber of Level of studies evidence non-randomised trials, cohort - studies, time series matched+ case-controlled studies. non-experimental studies Opinions
  43. 43. Internal Coherence: The critical appraisal -Consists in determining the possibility of bias of the study. -checklists
  44. 44. Critical appraisal. general-Are the groups similar (homogeneity)?-Did it exist randomization?was it described?-Are the endpoints clearly defined?-Is the statistical study correct?-Are the conclusions according with theresults?-Are the results of this study appliable to mypatient(s)?
  45. 45. Critical appraisal. Review/MetanalysisAre the results valid?1. Did the review address a clearly focused issue?2. Did the review describe: the population studied? the intervention given? the outcomes considered?
  46. 46. Critical appraisal. Review2. Did the authors select the right sort of studies for thereview? The right studies would: address the reviews question  have an adequate study design
  47. 47. Critical appraisal. Review3. Do you think the important, relevant studies wereincluded?Look for: which bibliographic databases were used personal contact with experts search for unpublished as well as published studies search for non-English language studies
  48. 48. Critical appraisal. Review4. Did the reviews authors do enough to assess thequality of the included studies? Did they use: description of randomization?  rating scale?
  49. 49. Critical appraisal. ReviewWhat are the results?5. Were the results similar from study to study? Are the results of all the included studies clearlydisplayed? Are the results from different studies similar? If not, are the reasons for variations between studiesdiscussed?
  50. 50. Critical appraisal. Review 6. What is the overall result of the review? Is there a clinical bottom-line? What is it? What is the numerical result?
  51. 51. Critical appraisal. Review 7. How precise are the results? Is there a confidence interval?
  52. 52. Critical appraisal. ReviewCan I use the results to help my patient?8. Can I apply the results to my patient?Is this patient so different from those in the trial thatthe results don’t apply?
  53. 53. Critical appraisal. Review9. Should I apply the results to my patient?how great would the benefit of therapy be for thisparticular patient? Is the intervention consistent with my patients values andpreferences? Were all the clinically important outcomes considered? Are the benefits worth the harms and costs?
  54. 54. Critical appraisal. Treatment.Is the research valid?1a. Was the assignment of patients to treatments randomized?1b. Was the randomization list concealed?1c. Were subjects and clinicians ‘blind’ to which treatment wasbeing received?
  55. 55. Critical appraisal. Treatment.2a. Were all subjects who entered the trial accounted for at its conclusion?2b. Were they analyzed in the groups to which they were randomized?
  56. 56. Critical appraisal. Treatment.3a. Aside from the experimental treatment, werethe groups treated equally?3b. Were the groups similar at the start of thetrial?
  57. 57. Critical appraisal. Treatment.Is the research important? RRR (Relative risk reduction) ARR (Absolute risk reduction) NNT (Number needed to treat)
  58. 58. Critical appraisal. Treatment.Can I apply it to my patient?4. Is this patient so different from those in the trialthat the results don’t apply?
  59. 59. Critical appraisal. Treatment.5a. How great would the benefit of therapy be for thisparticular patient?5b. What is the event rate in my practice for patients likethis one?
  60. 60. Critical appraisal. Treatment.Is it consistent with the patients values andpreferences?6. Do I have a clear assessment of the patient’s valuesand preferences?
  61. 61. Critical appraisal. Treatment.7. Do this intervention and its potential consequencesmeet them?
  62. 62. Critical appraisal. DiagnosisIs the research valid?1. Was there an independent, blind comparison with areference ("gold") standard of diagnosis?
  63. 63. Critical appraisal. Diagnosis2. Was the diagnostic test evaluated in an appropriatespectrum of patients (like those in whom it would beused in practice)?
  64. 64. Critical appraisal. Diagnosis3. Was the reference standard applied regardless of thediagnostic test result?
  65. 65. Critical appraisal. Diagnosis Is the research important?SensitivitySpecificity
  66. 66. Critical appraisal. DiagnosisCan I apply it to my patient?4. Is the diagnostic test available, affordable,accurate, and precise in your setting?
  67. 67. Critical appraisal. Diagnosis5. Can you generate a clinically sensible estimate ofyour patients pre-test probability (from practice data,from personal experience, from the report itself, or fromclinical speculation?)
  68. 68. Critical appraisal. Diagnosis6. Will the resulting post-test probabilities affect yourmanagement and help your patient? (Could it moveyou across a test-treatment threshold?)
  69. 69. Critical appraisal. Prognosis/harmIs the research valid?1. Was a defined, representative sample of patientsassembled at a common (usually early) point in thecourse of their disease?
  70. 70. Critical appraisal. Prognosis/harm2. Was patient follow-up sufficiently long andcomplete?
  71. 71. Critical appraisal. Prognosis/harm3. Were objective outcome criteria applied in a"blind" fashion?
  72. 72. Critical appraisal. Prognosis/harm4. If subgroups with different prognoses areidentified, was there adjustment for importantprognostic factors?
  73. 73. Critical appraisal. Prognosis/harm5. Was there validation in an independent group("test-set") of patients?
  74. 74. Critical appraisal. Prognosis/harmIs the research important? Outcome Rate (95% CI) Probability (95% CI)
  75. 75. Critical appraisal. Prognosis/harmCan I apply it to my patient?6. Were the study patients similar to your own?
  76. 76. Critical appraisal. Prognosis/harm7. Will this evidence make a clinically important impacton your conclusions about what to offer or tell yourpatient?
  77. 77. After the critical appraisal youconclude that that article you´ve readhas a low-moderate-high probabilitiesto be biased
  78. 78. SummaryAfter you make a clinical question, youformulate correctly that question, lookfor the information , obtain theappropriate articles and make anappropriate critical appraisal, you getthe following answer:“there is a X level of evidence to assurethat the answer to our question wasyes/no”
  79. 79. frodriguezv14@hotmail.com frodriguezv@sego.es
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