Introduction of Evidence Based Medicine

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Introduction of Evidence Based Medicine

• ???
• ??????????

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?.??

• ???????????,?????access,interpret?apply,???clinici
  ans???????????,Evidence base Medicine(????)??????
• 1992?Gordon Guyatt?????McMaster???????EBM?1992?Joh
  n C. Simclair ? Mickael B. Bracken?????EBM???textb
  ook of Neonatology effective care of the newborn
  infant.

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EBM???

• The conscientious, explicit, and judicious use
  of current best evidence in making decisions
  about the care of individual patients.?
• What is EBM?
• EBM is the integration of best research
  evidence with clinical expertise and patient
  value

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????????????

• ??????????????(Asking answerable question)
• 1. well formed clinical question
• a. patient or problem(P)
• b. intervention(I)
• c. comparison intervention (if appropriate)(C)
• d. Outcome(O)

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???????????

• 2.Type of question
• clinical finding etiology differential
  diagnosis diagnostic test prognosis therapy
  prevention cost effectiveness quality of
  life.
• EX. In women caring babies of 24 to 34 weeks
  question who are threatening to deliver, does
  corticosteroid (dexa-methasone) compared with no
  treatment reduce the incidence RDS in their
  babies?

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?????????(finding the best evidence)

• Sources of evidence
• textbooks
• journals,
• conference proceedings
• Experts
• Electronic source ?CATs Best Evidence CoChrane
  Library Bibliographic database(Medline, CINAHL)
• ?Evidence ???????????,?systematic review???????

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?????????(finding the best evidence)

• Primary reports?Evidence ??MedLine???, search by
  using MeSH terms,text words, combining them with
  AND or OR,???methodological filters
  strategy ??????????????list of articles?

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?????????(finding the best evidence)

• ??Reviews ?article (?systematic reviews of the
  results of RCTs.)
• Studies of women with threatened preterm
  delivery that assess the effect of antenatal
  steroid on the incidence of RDS
• ?
• Typecorticosteroid AND respiratory
  distress syndrome AND (systematic review OR
  meta-anal) ???????articles.

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?????????(finding the best evidence)

• 4Shierarchical structure system,???

Evidence level of articles
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?????????????

• ?????????,???????????
• Step1Selection and sampling
• Step2randomization
• Step3follow up.??? 5Cs?-- Contamination,
  cross-over, compliance, co-intervention,
  count(loss to follow up)???bias.
• Step4outcome
• Step5analysis

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(1)Appraising therapy articles

• ?V(validity),I(importance), P(practice
  application)????appraisal.
• 1.Is the study valid? 
• clearly defined question?
• Concealed Randomized.
• intention to-treat analysis?
• research participators blinded
• groups treated equally
• Comparable group at the start of the trial?
• All patients account for at its conclusion

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(1)Appraising therapy articles

• 2. Are the results important?
•   Outcome
• Exposure Event No event
• Treated a b
• Control c d

• Treatment effect measures
• RR(relative risk) a / (ab) c / (cd)
• RRR(relative risk reduction) 1 - RR
• OR (odds ratios) ad / bc
• Risk difference(RD) a / (ab) - c / (cd)
• NNT 1/RD
• Calculation of 95 confidence interval

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(1)Appraising therapy articles

• 3. Incorporate your patients values and
  preferences into deciding on a course of action

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(2) Appraising diagnosis articles

• 1. Is the study valid?
• Clearly defined question?
• A validated test (Gold standard test)?
• Test evaluated on an appropriate spectrum of
  patient?
• Reference standard applied to all patients?

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(2) Appraising diagnosis articles

• 2. Are the results important ?
• What we thought before test information
  what we think after
• ? pretest probability likelihood ratio
  posttest probability

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(2) Appraising diagnosis articles
Disease - Disease - Disease -
Test Result a True positive b False positive
- c False negative d True negative
ab
cd
ac
bd

• Sensitivity a / (ac)
• ?MnemonicPID (Positive In Disease)
•  Specificity d / (bd)
• ?Mnemonic NIH (Negative In Health)
• positive predictive value a / (ab)  
   
• Negative predictive value d / (cd)

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(2) Appraising diagnosis articles

• ? predictive values change as the likelihood of
  disease changes .so need likelihood ratio
• LR ???
• Likelihood of a particular test result in someone
  with disease
• Likelihood of the same test result in someone
  without the disease
• MnemonicWOWO (With Over With Out)
• LR () Sensitivity true() /
  false()
• 1 - Specificity
• LR (-) 1 - Sensitivity false() /
  false(-)
• Specificity

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(2) Appraising diagnosis articles

• ??posttest probability?Steps
• Step1Estimate the pretest probability
• Step2Convert the pretest probability to pretest
  odds
• pretest odds pretest probability
• 1- pretest
  probability
• Step3Determine post-test odds
• ? post-test odds pretest odds LR
  (negative or positive)
• Step4Converting post-test odds to post-test
  probability
• ? posttest probability posttest odds
• 
  1 posttest odds

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(2) Appraising diagnosis articles

• ?predict pyloric stenosis by UltraSound
• if pretest probability 46,LR 77,LR-
  0.03,then,Post-test probability in Test is
  0.46/(1-0.46)77 66,then 66/ (1 66) 99
  (87100)?? posttest probability in Test- is
  0.46/(1-0.46) 0.03 0.256,then 0.0256 /
  (10.0256) 2.5 (0 12)???,UltraSound in
  predicting pyloric stenosis ????

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(2) Appraising diagnosis articles

• 3. decide to perform the test or not on the basis
  of your assessment.

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(3) Appraising prognosis studies

• 1. Is the study valid?
• Is the sample representative?
• Is the follow up long enough for the clinical
  outcome?
• Was follow up complete?
• Outcomes measured blind?

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(3) Appraising prognosis studies

• 2. Are the result important?
• What is the risk of the outcome overtime?

Outcome event Outcome event
Yes No
experiment a b
control c d
Relative risk a/ (ab) c/(cd) Odd ratio
(a b)/ (c d) Rare case? RROR
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• Odd ratio in case control study
• Risk present ? risk absent case group
• Risk present ? risk absent control group
• 1000 comparable patient
• ? ?
• Disease absent (500) Disease present (500)
• if risk present is 5 If risk present
  is 20
• risk absent is 95, risk absent is 80
• Disease present
• 20/80 (odds of risk being present)
  0.25
• Disease absent
• 5/95 ( odds of risk being present)
  0.05
• So,odds ratio 0.25/0.055

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(3) Appraising prognosis studies

• How precise are the estimate????95 confidence
  intervals around the odds ratio.
• ?Standard error(SE)
• v(p(1-p)/n)
• ??,p the proportion of the patients who
  experience the event
• ??,95 CI is P 1.96 SE()?

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(4)Appraising articles on harm/etiology

• 1. Is the study valid?
• Clearly defined research question?
• Similar group patients?
• Same exposure and clinical outcome measurements
• Follow up complete and long enough?
• Causative -link

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(4)Appraising articles on harm/etiology

• 2. Are the results important?
• In a cohort study
• Relative risk RRa/(ab)/ c/ (cd)
• In a case-control study
• Odds ratio OR ad / bc
• To calculate the NNH for any OR and PEER (patient
  expected event rate)
• NNHPEER(OR - 1) 1 / PEER (OR-1) (1-PEER)
• ?cohort study ?,??????NNT????reciprocal of
  the difference in adverse event rate.

exposure Adverse outcome Adverse outcome Adverse outcome
exposure Present (case) Absent (control)
exposure Yes a b
exposure No c d
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(4)Appraising articles on harm/etiology

• 3.Are the results applicable to your patients?

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(5) Appraising systematic reviews

• 1. Is the systematic review valid?
• High quality studies relevant to your question?
• Comprehensive search and how the reviewers assess
  the validity of each study?
• Are the studies consistent clinically and
  statistically?

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(5) Appraising systematic reviews

• ???, key features of a good review
• a.locate all original articles on the topic of
  interest
• b.clinical evaluation of the reports
• c.conclusion from a synthesis of studies which
  meet pre-set quality criteria (meta-analysis)

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(5) Appraising systematic reviews

• 2. Are the results important ?
• ?review?odds ratio ,?
• NNT 1 - PEER (1 - OR )
• (1 - PEER) PEER (1 - OR )
• 3.Do the results apply to my patients?

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????????valid,important??????????????????

• ??
• Are your patients similar to those of the study ?
• The study effect on your patient
• a. for diagnostic test ? pretest probability
  (prevalence)??post-test probability.
• b. for therapy ???PEER??
• NNT(for your patient)1/ (PEER RRR)

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????????valid,important??????????????????

• Is the intervention realistic in your setting?
• Does the comparison intervention reflect your
  current practice?
• What alternative are available?
• Are the outcomes appropriate to your patient?

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• Guidelines Development
• Cost and Effect Analysis
• Decision Analysis

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Qualitative Research

• A small child runs in from the garden and says,
  excitedly, Mummy, the leaves are falling off the
  trees. Tell me more, says his mother. Well,
  five leaves fell in the first hours, then 10
  leaves fell in the second hour..
• That child will become a quantitative researcher!

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Qualitative Research

• A second child, when asked tell me more, might
  reply, Well, the leaves are big and flat, and
  mostly yellow or red, and they seem to be falling
  off some trees but not others. And, Mummy , why
  did no leaves fall last month?
• That child will become a qualitative researcher!

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????????(Evaluation and Audit)

• ?????????self-evaluation,???????????????????
  ??????????????????????????knowledge??????EBM?team
  ,???????

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????Evidence-Based Clinical practice????

• EBM???clinical skill,??????????????,?????????????
  ,?????????????????????,??????????????????EBM??,??
  practice guideline?consensus recommendation.

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????Evidence-Based Clinical practice????

• ??EBM???????(1)????????????????,???????(2)??????
  ???????????????,???????(3)??EBM work???????

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????

• Evidence-Based Medicine ??????????????????????????
  ????,????,????,???????????????,?????????????????,?
  ?????????,?????????????,????????????????,?????????
  

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????EBM???

• 1996???,???????Oxford EBM??,????EBM?
• ?VS(????????????????????)?Oxford, Australia???
• ??EBM Center
• ????link?England
• EBM?????????

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????EBM???

• ???????????????????????EBM??
• ??EBM??
• ??/???/???/???/??
• ????EBN
• ???EBP

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????EBM???

• PBLEBM style ?journal reading in ???/???/???
• PGY1,R3,CR?VS?EBM??????(??PGY1 36????????????)
• ???,??critical appraisal???
• ??EBM????????????

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????EBM???

• ??EBM???
• 1.?????
• 2.??????????critical appraisal
• 3.??????????
• 4.???????

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????(??) ??????(??)
?? ?????? ??EBM??,?????????? ?????? ????
?? ?????????(?????????) EBM??????? ???
???? ??????,??????? EBM?????????? EBM????????
?? ??????? ??????? ???????? ?????(????) ??????? ????/????
????????
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• Epidemiologist?Biostatistician
• ??????
• ????