Introduction to EBM

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Introduction to EBM

• There are three kinds of lies  lies, damned
  lies, and statistics
• Benjamin Disraeli, British PM, 19th Century

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Why Should I Practice Evidence Based Medicine?

• You should practice evidence based medicine
  because intuition, pathophysiologic rationale,
  and anecdotal experience are insufficient grounds
  for clinical decision making.

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Intuition

• Since menopausal women and age-matched men have
  equal rates of heart disease, but pre-menopausal
  women have less heart disease than age-matched
  men, intuition might lead you to believe that
  estrogen is cardio-protective
• Long term estrogen replacement was prescribed
  routinely for primary cardiac prevention in
  menopausal women

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The Evidence

• Estimated hazard ratios (HRs) (nominal 95
  confidence intervals CIs) were as follows CHD,
  1.29 (1.02-1.63) with 286 cases
• Trial stopped early due to increased adverse
  events in study group, including CHD
• Risks and benefits of estrogen plus progestin in
  healthy postmenopausal women principal results
  from the Women's Health Initiative randomized
  controlled trial. JAMA 2002 Jul 17288(3)321-33.

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Pathophysiologic Rationale

• Pathophysiologic rationale would lead you to
  believe that Beta Blockers would be detrimental
  in patients with congestive heart failure
• It would also lead you to believe that
  anti-arrhythmic drugs would save lives after
  myocardial infarction
• Beta blockers were routinely avoided in patients
  with systolic dysfunction, while a bag of IV
  lidocaine was routinely hung for post-MI patients

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The Evidence

• All randomized clinical trials of beta-blockers
  versus placebo in chronic stable congestive heart
  failure were included
• A hierarchical random-effects model was used to
  synthesize the results. A total of 22 trials
  involving 10 135 patients were identified. There
  were 624 deaths among 4862 patients randomly
  assigned to placebo and 444 deaths among 5273
  patients assigned to beta-blocker therapy
• Beta-blockers in congestive heart failure. A
  Bayesian meta-analysis. Ann Intern Med 2001 Apr
  3134(7)550-60.

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Anecdotal Experience

• I gave a patient IV iron once and he nearly
  died, Ill never do that again. Anonymous Wake
  Med attending, 2003
• Physicians have been frightened by harmful
  effects of traditional IV iron preparations (iron
  dextrans)

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The Evidence

• For sodium ferric gluconate complex in sucrose,
  there were no reports of deaths over the entire
  period (1976 to 1996). However, for iron
  dextrans, there were 31 fatalities among 196
  allergy/anaphylaxis cases reported in the United
  States between 1976 and 1996, yielding a
  case-fatality rate of 15.8. These data show that
  sodium ferric gluconate complex in sucrose, when
  compared with iron dextrans in comparably sized
  patient usage populations with similar total
  rates of reporting of allergic events, has a
  significantly lower reported mortality rate (P lt
  0.001)
• Sodium ferric gluconate complex in sucrose safer
  intravenous iron therapy than iron dextrans. Am J
  Kidney Dis 1999 Mar33(3)464-70.

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Statistics Can Be Misleading

• Say you were standing with one foot in the oven
  and one foot in an ice bucket.  According to the
  percentage people, you should be perfectly
  comfortable.  Bobby Bragan, 1963
• The average human has one breast and one
  testicle.  Des McHale

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The Biggest Misconception about EBM

• I dont have time to read Journals. They stack
  up on my desk, I get really annoyed and feel
  guilty every time I look at them eventually when
  the stack gets high enough I just throw them all
  away.
• You shouldnt be reading journals page for page.
  EBM is not about reading journals.

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EBM is about your patients

• What is the best therapy for this patient?
• Will my therapy harm this patient?
• What is this patients prognosis?
• How can I diagnose whats wrong with this
  patient?
• We have an obligation as physicians to know these
  answers, or at least how to find them.

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The 4 Paper Types of EBM

• The 4 types of paper we utilize are therapy,
  harm, diagnosis, and prognosis papers. EBM is
  about knowing how to use the literature to find
  answers to the above questions, such that you
  dont end up relying on intuition,
  pathophysiologic rationale, and anecdotal
  experience to make decisions

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Therapy Paper

• Ideally Randomized Controlled Trial (RCT)
• Ideally prospective
• Look closely at endpoints
• Beware composite endpoints
• The therapy doesnt have to be a drug. e.g.
  banding of varices, stenting of arteries,
  surgical procedure
• Results should include ARR and NNT
• Beware RRR

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Harm Paper

• Never start out as harm trials (that would be
  unethical)
• You cant randomize one group to cigarettes and
  one to placebo
• Rather, these are usually either retrospective
  cohort or case-control studies
• e.g. Looking back at two groups similar except
  for smoking hisotry
• Or, preferably, RCTs in which the therapy is
  incidentally found to cause harm

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In clinic and on the wards this year, challenge
yourself by asking the questions

• Why am I giving this medicine?
• Is there any risk of harming the patient with
  this medicine?
• Why am I ordering this test?
• How good is this test?
• Is there any risk of harming the patient with
  this test?
• How will the test result change my management of
  this patient?
• How will the test result change my patients
  prognosis?
• How can I diagnose the condition I suspect?
• Am I satisfied that I have ruled out the
  condition I suspected with this negative test?

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Often you will know the answer to the question

• But if you are in a situation where you are
  stumped, or you are doing something
• because thats what everybody else does or
• because thats what my attending said to do or
• because its Tuesday or
• I have no idea why Im doing this..
• then you just found your next EBM presentation!

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How do we form a clinical question to search the
literature for answers?

• PICOT. This is a critically important skill. If
  we dont PICOT effectively, we wont find the
  answer we seek.
• P patient population
• I intervention
• C comparison
• O outcome
• T type of study

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PICOT Examples

• Dr. So Yoon Jang admitted a patient to Med B with
  the diagnosis of acute lupus nephritis. She
  wondered whether to use IV cyclophosphamide or
  oral mycophenolate mofetil as the initial
  treatment.
• Patient population P in female patients with
  acute lupus nephritis
• Intervention I does oral mycophenolate
  mofetil
• Comparison C compared to IV cyclophosphamide
• Outcome O reduce mortality (or induce more
  remission, or prevent the need for dialysis,
  or whatever you want the outcome to be)?
• Type of study T therapy

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PICOT Examples

• Dr. Keith Golden has a 50 year old male clinic
  patient who is terrified of colonoscopy. The
  patient (and Dr.Golden) wonder if virtual
  colonoscopy is as effective as colonoscopy for
  screening, without the risk of colon perforation.
  
• P in patients at average risk for colon cancer
• I is CT colonography
• C compared to colonoscopy
• O as sensitive for detecting colon polyps (or
  colon cancer, or whatever)?
• T diagnosis