CLINICAL EPIDEMIOLOGY

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CLINICAL EPIDEMIOLOGY

and EVALUATING MEDICAL EVIDENCE
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Nasser Gayed, MD MPH

• Professor, Dept of Medical Information Science,
• COM at UC
• Teaching course since 1990.
• Course Director since 2000.

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Why do I need to learn epidemiology?

• How much epidemiology does the average medical
  student need to know?
• If epidemiology has to do with epidemics the
  answer is
• Very little

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I dont teach epidemiology

• What do I teach?
• Why is it called epidemiology?
• Why you need to know it?

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What do I teach?

• The methods of clinical research
• The rules of evidence in evidence based
  medicine

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• Critical reading is a basic tool of the
  practicing physician for keeping his or her
  practice consistent with current medical
  knowledge. The two main goals of this course are
• To make students believe in the importance of
  being able to evaluate medical research studies.
• To provide them with the tools to do so.

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Why is it called epidemiology?
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For thousands of years

• Clinicians did not deal with numbers,
  frequencies, distributions. Why?
• Epidemiologists did
• epidemiology paragraph
• No one else had tools for clinical research

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• All who drink of this treatment recover in a
  short time, except those whom it does not help,
  who all die. It is obvious, therefore, that it
  fails only in incurable cases.
• Galen c.199

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• Clinical research only started in the middle of
  the 20th century
• Researchers started using the tools of
  epidemiology to study chronic diseases. Example.
• This made those tools more relevant and useful to
  clinicians (and medical students).
• This also expanded and defined the new discipline
  of Clinical Epidemiology

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Case in point

• Journal of Chronic Diseases established in 1955
• In 1987 they added a subtitle A Forum for
  Clinical Epidemiology
• In 1988 it became Journal of Clinical
  Epidemiology

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Clinical Epidemiology

• Became the home of the methodology of clinical
  research

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• Used to be The leaders of each specialty were
  experienced clinicians.
• Now It is those who publish important clinical
  trials. Those are for the most part
  epidemiologists.

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These are the people in charge of

• Medical schools
• Residency programs
• Fellowship programs
• Faculty appointments and promotions
• Grant approvals
• And more

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Why you need to know it?Sally Hoskins
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Why you need to know it?

• Atrial fibrillation
• Atrium does not contract
• Mitral Stenosis
• Dilated
• Blood clot
• Warfarin (Coumadin)
• Non-valvular AF
• If TIA/CVA then warfarin

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• Warfarin for all? Is aspirin enough?
• Randomize to Warfarin, ASA, or placebo.
• Many contraindications
• Exclusion criteria

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• Still many should not be on warfarin. Exclusion
  criteria not enough.
• How many?
• A whole lot!
• What then?
• Patients own clinician to approve.
• Lets do it

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Meeting with clinicians

• Warfarin better. Abstract.
• Clinicians Many patients should not be on
  warfarin. Now they might.
• Reply Why? During our study there were patients
  that should not be on warfarin and they didnt
  receive warfarin.
• Clinicians Yes, but that was before there was a
  study in a prominent journal that reads
  ..warfarin was superior to aspirin and placebo

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• Who will protect these patients?
• Reply Their own clinicians just like you guys
  did.
• Clinicians But that is only if they read more
  than the abstract.
• And, if they know what to look for and know what
  it means.

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Reply

• Dont you guys teach them that stuff in medical
  school?!
• The End

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SPAF Trial

• Stroke Prevention in Atrial Fibrillation
• 627 patients were randomized to warfarin,
  aspirin, or placebo
• Warfarin was superior.

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Average Clinicians Conclusion

• Every patient with atrial fibrillation who
  doesnt have any of the exclusion criteria should
  receive warfarin.
• You would reach that conclusion if you read the
  articles abstract and conclusion.

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My Conclusion

• Not every patient with atrial fibrillation should
  be started on warfarin.
• My reason?
• I read the whole article.
• What did I find?

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They Started with 18,376 Patients!

• Thats not bad by itself.
• Most were excluded for appropriate criteria
• BUT among the excluded
• 717 refused
• Another 1,084 their doctors refused
• Another 2,262 no reason was recorded
• Another 239 patient or doctor refused
  anticoagulation. (So they were randomized into
  the aspirin versus placebo trial.)

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Compare These Numbers

• 717 refused
• Another 1,084 their doctors refused
• Another 2,262 no reason was recorded
• Another 239 patient or doctor refused
  anticoagulation. (So they were randomized into
  the aspirin versus placebo trial.)
• To 627 randomized (210 ended on warfarin)