Transcript BECOMING AN INFORMATION MASTER-or-

BECOMING AN
INFORMATION
MASTER-or-
How to feel good about not knowing
everything
AGENDA
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Context and some philosophy
Learn what is: ‘patient-oriented’ evidence
Asking clinical questions
Look at a couple examples from therapy articles
Learn to calculate some things
Practice calculating some things
Learn what the numbers mean for practice
If time, some searching
EVIDENCE BASED
MEDICINE
The judicious and conscientious use of current
best evidence from medical care research in
making decision about the care of individuals.
DEFINITION FOR THE 21ST
CENTURY
• a set of tools and resources for finding and
applying current best evidence from research for
the care of individual patients.
• “evidence based medicine seeks to empower
clinicians so that they can develop independent
views regarding medical claims and
controversies”
The Problem
• “In family medicine it was recently estimated
that a physician would need to spend 627.5
hours just to read the 7287 articles relevant to
primary care published each month”
HOW DO WE MAKE CLINICAL
DECISIONS?
Clinical expertise
Research
Evidence
Patient’s
preferences
The bigger picture
• More health care does NOT equal more health
• Diminishing returns on health care spending
beyond $1000/capita/year
• How much does Canada spend?
• How likely is a BP patient in family medicine to
be on a thiazide diuretic ($) compared to ACE-I
in a specialist setting ($$$)?
APPLICATION OF EBM TO
PRIMARY CARE
• Review of the literature on patient centered
care:
– Patient satisfaction is the highest when they take part
fully in decision making
– Patient compliance with the strategy is better when
the decision has been made in partnership
APPLICATION OF EBM TO
PRIMARY CARE
Clinical Expertise (I.e. Parachute prevents death!!)
There will never be an RCT to prove that Pap screening reduced
cervical cancer or that cigarette smoking causes lung cancer
Patient-oriented evidence?
Anti-depressants may benefit some patients with
inflammatory bowel disease
by Suzanne Morrison
May 02, 2008
VS
Acarbose in the prevention of cardiovascular
disease and hypertension in patients with
impaired glucose tolerance
THE WELL BUILT CLINICAL
QUESTION
• Anatomy of a question: PICO
P- What is the type of patient or problem
to be addressed
I- What is the intervention or exposure being
considered?
C- What is the comparison intervention or
exposure (if relevant)
O- What are the clinical outcomes of interest
Example of a POEM (CMA)
Level of evidence = A
Acarbose is effective in the prevention of cardiovascular events and hypertension in
patients with impaired glucose tolerance.
In an international, multicentre trial 1, 1429 patients with a mean age of 54.5 years and
BMI 30.9 were randomized to receive either acarbose 100 mg 3 times a day or placebo.
Decreasing prostprandial hyperglycemia with acarbose was associated with a 2.5%
absolute risk reduction and a 49% relative risk reduction in the development of
cardiovascular events (HR 0.51, 95% CI 0.28 to 0.95), and a 5.3% absolute risk reduction
and 34% relative risk reduction in the incidence of new cases of hypertension (HR 0.66,
95% CI 0.49 to 0.89). The risk reduction was no influenced by adjusting for major risk
factors.
References
1.Chiasson JL, Josse RG, Gomis R, Karasik A, Laakso M, for the STOP-NIDDM Trial Research Group. Acarbose treatment and the risk of
cardiovascular disease and hypertension in patients with impaired glucose tolerance. JAMA 2003;290:486-494
What did those numbers mean in
practice?
Consider a study in which 15% (0.15) of the control
group and 10% (0.10) of the treatment group died after
2 years of treatment. The results can be expressed in
many ways as shown below.
Measure
Meaning
Relative risk (RR)
RR how many times more
likely it is that an event will
occur in the treatment group
relative to the control group.
RR = 1
•no difference between the 2
groups
RR < 1
•treatment reduced the risk
of the outcome
RR > 1
•treatment increased the risk
of the outcome
• risk of outcome in
the treatment group
divided by the risk
of outcome in the
control group
Example
RR = 0.1/0.15
= 0.67
Since RR < 1, the
treatment decreases
the risk of death
Measure
Meaning
Example
Absolute risk reduction
(ARR)
ARR tells us the absolute
difference in the rates of
events between the two
groups and gives an
indication of the baseline
risk and treatment effect.
ARR = 0 means that there
is no difference between the
2 groups (thus, the
treatment had no effect)
ARR = 0.15-0.10
= 0.05 (5%)
• risk of outcome in the
control group minus risk
of outcome in the
treatment group (also
known as the absolute
risk difference)
•The absolute benefit of
treatment is a 5%
reduction in the death
rate.
Measure
Meaning
Relative risk
reduction (RRR)
RRR tells us the
RRR = 0.05/0.15
reduction in rate of the
= 0.33
outcome in the treatment
(33%)
group relative to the
control group.
By HOW MUCH did the
OR
intervention improve the
outcome?
•=ARR divided by
the risk of outcome
in control group (or,
1 - RR)
Example
1-0.67 = 0.33 (33%)
Measure
Meaning
Example
Number needed to
treat (NNT) =
1/ARR
NNT tells us the
number of patients
we need to treat with
the treatment under
consideration in
order to prevent 1
bad outcome.
NNT
= 1/0.05
= 20
•We would need to
treat 20 people for 2
years in order to
prevent 1 death.
Let’s do an example on the board
Patients Understand pictures better than RRR, NNT
What are the numbers for our example?
Knowing how to use your time
wisely
Look at literature similar to a
Drug Rep
• Pharmaceutical "reps" are now much more informative
than they used to be, but they may show ignorance of
basic epidemiology and clinical trial design
• The value of a drug should be expressed in terms of
safety, tolerability, efficacy, and price
• The efficacy of a drug should ideally be measured in
terms of clinical end points that are relevant to patients;
if surrogate end points are used they should be valid
• Promotional literature of low scientific validity (such as
uncontrolled before and after trials) should not be
allowed to influence practice
• identify, for this patient, the ultimate objective of
treatment (cure, prevention of recurrence, limitation of
functional disability, prevention of later complications,
reassurance, palliation, relief of symptoms, etc);
• select the most appropriate treatment, using all available
evidence (this includes considering whether the patient
needs to take any drug at all); and
• specify the treatment target (to know when to stop
treatment, change its intensity, or switch to some other
treatment).
E.g. hypertension
• the ultimate objective of treatment is to prevent
(further) target organ damage to brain, eye, heart,
kidney, etc (and thereby prevent death);
• the choice of specific treatment is between the various
classes of antihypertensive drug selected on the basis of
randomised, placebo controlled and comitemtive
trials—as well as non-drug treatments such as salt
restriction; and
• the treatment target might be a phase V diastolic blood
pressure (right arm, sitting) of less than 90 mm Hg, or
as close to that as tolerable in the face of drug side
effects.
Good surrogate endpoint
• The surrogate end point should be reliable, reproducible, clinically available,
easily quantifiable, affordable, and show a "dose-response" effect (the higher
the level of the surrogate end point, the greater the probability of disease)
• It should be a true predictor of disease (or risk of disease). The relation
between the surrogate end point and the disease should have a biologically
plausible explanation
• It should be sensitive—a "positive" result in the surrogate end point should
pick up all or most patients at increased risk of adverse outcome
• It should be specific—a "negative" result should exclude all or most of those
without increased risk of adverse outcome
• There should be a precise cut off between normal and abnormal values
• It should have an acceptable positive predictive value—a "positive" result
should indicate a high likelihood of the outcome
Database searching for evidence
• Pubmed clinical queries (single articles, specific)
• Health Knowledge Central (general site
compiling other resources)
• Cochrane database (high quality for therapy but
not many topics)
• Bandolier (critically appraised for you)
• E-medicine
• Up to date
Search questions?
• Treatment of subclinical hypothyroidism?
• 42 year old patient with sudden onset of severe
hypertension refractory to treatment. - Who
should be screened for secondary causes of
hypertension?
• 60 year old woman with ‘squeezing’ chest pain,
controlled hypertension- is an ECG useful to
determine need to go to ER?