Transcript evidence-based preventive medicine

EVIDENCE-BASED
PREVENTIVE
MEDICINE
A. Albert Tripodi, M.D.
Class Schedule
1. Introduction and definitions: what is “evidence”
2. Diabetes and metabolic syndrome
3. Hypertension
4. Cholesterol and Cardiovascular disease
5. Cancer and it’s prevention
6. Geriatrics and “end of life care”
7. Complementary and alternative medicine and
nutrition
8. Selected short subjects : arthritis, osteoporosis,
delivery of health care
My Objectives
To provide tools for evaluation of
“evidence”
 To be aware that today’s “facts”
may become tomorrows fallacies
 To be systematic and critical
 To have tools for the evaluation
of your own medical care

Phronesis



Phronesis is the highest level of wisdom.
Phronesis is the ability to discern the correct
action when there is insufficient evidence to
determine the correct action.
Aristotle
Sources of “Evidence”



Peer reviewed Journals (JAMA, NEJM,
BMJ, Lancet, etc.)
Publications from Medical schools
and clinics (Mayo, Cleveland,
Harvard, etc)
Governmental – National Library of
Medicine (Medline), NIH (National
Institutes of Health), CDC (Center for
Disease Control)., Cochran data base
Lay Press



Tuesday NYT – “Science Times” (Jane
Brody’s column).
Sarasota Herald Tribune – daily, Dr.
Paul Donahue
Internet: Pubmed.gov; AHRQ.gov
(Agency for Healthcare research and
Quality); medscape.com; WebMD;
CDC.gov; NIH.gov; Harvard,Mayo,
Johns Hopkins.
DEFINITIONS



Medicine: Study of the human condition
(biology, physiology, chemistry, physics,
pathology, psychology, pharmacology)
Prevention: Keeping bad things from
happening (prolonging the “quality” of life).
Primary vs. secondary.
Evidence: Scientific method, statistical analysis,
probability, meta-analysis, placebo effect.
SCIENTIFIC METHOD
 Hypothesis
(question)
 Method (experiment)
 Observation (data)
 Conclusions (analysis)
Science




All scientific knowledge is relative, not
absolute.
Science deals with probability and makes
generalizations and relies on statistics.
All generalizations are theories, rather
than facts.
No other method of inquiry has been
found as reliable as the scientific method.
 Risk
vs. Benefit
 Probability – of a test to be
useful, a medication to work,
a diagnosis to be correct, or a
prevention to be beneficial.
 P value – 95% certainty
STUDY EVALUATION






Reproducible results
Probability of being wrong – P value
Statistical power; the probability of
demonstrating a difference if a difference
truly exists
Statistical significance; the strength of
recommendation
Meta analysis
Placebo effect (control group)
TRIAL CRITERIA
Randomized, controlled, clinical trial (RCT)
Is the “gold standard”
 Double blind
 Inclusion – exclusion criteria
 How are “drop-outs” or “lost to followup” handled
 Statistical analysis – p-value, power, RRR, ARR,
NNT
 Author’s analysis and recommendations ,
(applicable and generalisable?)

The Essence of a Controlled
Study
Two or more “treatments”
 Subjects selected from the broad
population at random
 Subjects have an equal chance
of being in each group.
 Causation is best established by
a controlled study (correlation
does not equal causation)

Important Terms
Reproducible results
 Sensitivity – The probability of
an abnormal test result among
those with disease.
 Specificity – the probability of a
normal test result among those
without disease.

More terms
ARR – absolute risk reduction
 RRR – relative risk reduction
 NNT – number needed to treat to
produce one clinically significant
result e.g. save one life or
prevent one heart attack
 NNH – The number needed to
treat before harming one person

ALTERNATIVES TO EVIDENCE
BASED MEDICINE








Eminence-based – “experience”
Vehemence-based
Eloquence-based
Providence-based
Diffidence-based
Nervousness-based
Confidence-based
“It won’t hurt to try!”
Clinical Trials
RCCT give confidence in the
conclusions.
 Animal studies first
 Phase I – small study on humans
to determine dose and toxicity.
 Phase II – larger study that
restricts eligibility, shows efficacy
and may be randomized.

Clinical Trials
continued
 Phase
III – large, randomized,
multicentered, established
efficacy and toxicity, and,
hopefully new standard of Rx.
PRINCIPLES OF MEDICINE
Everything is always worse than you
thought it was going to be.
Nothing is ever as simple as it first
seems.
A conclusion is the place where you
get tired of thinking.
THERE IS NO SUBJECT,
HOWEVER COMPLEX, WHICH
IF STUDIED WITH PATIENCE &
INTELLIGENCE, WILL NOT
BECOME MORE COMPLEX
Critical Thinking
The smaller the study the more room
for random error.
 Be aware that emotions play a role
in analyzing information.
 Uncertainty exists.
 The more a subject is controversial,
the greater the chance for bias.

PRIMUM NON NOCERE
“First Do No Harm”
 “But
tell me, is your physician
a money maker, an earner of
fees, or a healer of the sick”

Plato’s “Republic”

341 BCE
Improvement in Life Expectancy in
the 20th Century
1.
2.
3.
4.
5.
6.
7.
Public Health – sanitation, clean water , pasteurization
Adequate food supply
Immunization, public safety
Hygiene
Behavior modification : avoid nicotine, alcohol abuse,
narcotic abuse, eat breakfast, get 7-8 hours sleep, exercise
3 hours/week, keep weight within 10% of ideal (female =
105 + 5lbs for each inch in height over 60”; males 110 + 6
lbs for each inch over 60”), use seat belts, don’t text while
driving.
The average life expectancy after reaching age 80 in 1600
was six years; in 1980 it was 8 years( not necessarily
“quality” years.)
The Law of Diminishing Returns applies
The expert is seldom
in doubt but often in
error
Primary prevention
vs.
Secondary prevention
Pray to God,
but pick a good internist