Evidence based practice
Evidence based practice
Clinical Epidemiology
The roots of EBP are in Epidemiology.
Use of studies to evaluate populations,
treatments, testing, and therapies.
Looking for outcomes, diagnosis and
prognosis information that can be used
in patient care.
What studies can do this?
 Experimental
 Observational
The type of study used, depends upon
the information being sought.
Experimental or Observational?
Were exposures assigned by
investigators? Once this happens the
study becomes experimental.
If a natural course of the disease is being
followed without interference by the
investigator, the study is observational.
Which type of study is the best?
Experimental are useful for clinical
knowledge in treatment choices such as
as what type of treatment, what dose,
how long to treat.
Observational studies lead to
knowledge of the disease such as to the
etiology and risk factors. Who gets the
disease? What are the risks for
morbidity and mortality?
Experimental Studies
1.
Non Randomized trial: subjects are
knowingly assigned to the control or trial
group. This can lead to bias in the findings as
assignments are made.
2.
Randomized trial: The subjects are assigned
to groups in a masked/blinded fashion: be it
single, double blind or triple blind. This
leads to less bias in the findings. Not
appropriate with toxic or carcinogenic
agents, it would be unethical to assign a
known carcinogen as treatment.
Randomized Clinical Trial
Study Population
Randomly
Assigned
Current
New Treatment
Treatment
Do not Improve
Do not improve
Improve
Improve
Use of Randomized trials
 New drugs
 Non medication treatments of disease
 New technology
 Screening programs
 New ways of organizing care
 New delivery services
 Randomized clinical trials are more for
patient care as compared to Randomized trials
which may gather non clinical information.
Selection of subjects in a random study
Should be well documented in writing
and direction so others may follow in
the future.
No element of subjective decision
making on the part of the investigator
as to whom is included or not.
We want to trust the results and be able
to repeat them.
Masking or Blinding
 Once subjects are assigned they should not
know which group they are being assigned to.
 Placebos may be used to help mask.
 The observers or data collectors should not
know which group a patient is in or the
subject. “Double blinding”.
 In a triple blinding; subject, data collectors
and data analyzers do not know who is in
which group.
Crossover
 Planned crossover: after being on treatment
for a while, the patient is crossed over to the
other therapy and observed with it. Each
patient acts as their own control.
 Carryover from previous therapy must be
accounted for. (prostaglandin use in
glaucoma) Also patient enthusiasm may be
better for first treatment.
 Unplanned crossover: subjects change
treatment during study by subject choice or
clinician.
Generalizing the results of the study to
the general population
 Internal validity: study was properly
done without major methodologic
problems. The study size was good,
comparison groups were valid.
Findings are valid.
 External validity: the new therapy is
better for the disease treatment
regardless of where the patients are
treated, not just for the study group. It
can be generalized to the entire
population.
Publication bias
 Not all results of clinical studies are published
 Erroneous conclusions may be drawn if only
one side is published.
 Dramatic results are more likely to be
published.
 Funding may affect what is published.
 All clinical trials of medical interventions
must be registered in a public trial registry
before any participants are enrolled.
Types of Observational Studies
Are groups set up and chosen to be
observed?
Yes…..this becomes an analytical study as
now comparisons are being made
between the two groups.
No……this becomes a descriptive study
and usually is used to develop
hypothesis for future studies.
Types of observational study designs
 Cohort study: analytical study
 Case-control study: analytical study
 Cross-sectional study: analytical study
 Case study: descriptive study
Analytical Observational Studies
The direction of the study determines the type of
study:
1.
2.
3.
If you first look for exposure, and then
check the outcome: Cohort Study. This is
good to find causal relationships.
If you first look at the outcome and then go
back and check for exposure, this is a Case
Control study and is good for studying rare
diseases.
If you look at the exposure and the outcome
at the same time, this is a Cross-Sectional
study and you can identify prevalence with
it.
Cohort study
 A group of exposed individuals and a group of
nonexposed individuals are identified and
followed up on to compare the incidence or
rate of death from disease in the two groups.
 If a positive association exists between the
exposure and the disease, the proportion of
the exposed in whom the disease develops
should be greater than in the nonexposed
group. Great for finding the cause of a disease.
Cohort compared to Randomized
Studies
 Both studies compared exposed and non
exposed groups.
 Studies with harmful exposures can not be
randomized such as carcinogens, so cohorts
can be used ethically. Lifestyle choices lead to
some people having desired exposure for
study.
 When not performing a randomized study
questions are often left unanswered. Are
other factors besides the tested exposure
leading to conclusions?
Cohort Studies
Defined
Population
Nonrandomized
Exposed
Disease
No disease
Not Exposed
Disease
No disease
Prospective Cohort Study
 Also called concurrent cohort or
longitudinal study.
 A defined population is chosen and then
followed over time. First seeing who
develops the disease and then what
course the disease takes.
 This type of study takes many years.
 Exposure and nonexposure are found as
they occur during the study.
Retrospective Cohort Study
 Also called historical cohort study or
nonconcurrent prospective study.
 Use past data and histories to establish data.
 Exposed and nonexposed cases are still
compared, less time is needed.
 Exposure is ascertained from past records and
outcome is known when the study begins
from existing records.
Case-Control Studies
 Comparison is an essential component
of epidemiologic investigation, casecontrol study design uses comparison.
Diseased and healthy are compared.
Case studies do not.
Design of Case-Control Study
Cases
Have the disease
Were Were not
exposed exposed
Controls
Do not have the Disease
Were
Were not
exposed exposed
Sometimes a Case-Control study is
called a backward Cohort as in cohort
the exposure is first identified and then
the disease. Case-Control first
identifies the presence of disease and
then the exposure.
What case-control is not
 This is not a measurement of prevalence.
 The number of controls is chosen by the
investigator and does not reflect the
prevalence of the disease in the population.
 It is not a cohort test as the study begins with
people with the disease and compares them to
people without the disease. Cohort studies
work with exposed and non exposed people
and follows them for development of disease
over time.
 Case-control studies are valuable when
disease is rare.
 Cases may be easy to locate from
established records.
 Case-control studies are usually faster
than cohort studies.
When to use case-control studies
 First step when searching for cause of an
adverse health outcome.
 Compare people with disease and people
without the disease.
 Figure out which exposure or characteristic is
causing the disease.
 Once the relationship is documented, then a
more expensive cohort study may be done to
explore if exposure is linked to the disease.
Cross-sectional studies
 The characteristics of a population are
studied at one time point, this study
can be used to document prevalence.
 Exposures, disease and outcomes can all
be studied.
 Useful for determining health care
needs.
Archie Cochrane, MD
Archie Cochrane
 MD, Epidemiologist from Scotland
 In 1972 published: ”Effectiveness and
Efficiency” bringing attention to the bad
effects in health care from lack of available
evidence.
 “It is surely a great criticism of our profession
that we have not organized a critical
summary, by specialty or subspecialty,
adapted periodically, of all relevant
randomized controlled trials”
 An international systematic review of clinical
trials by specialty was his proposal for
improving health care.
 In the 1980s, Iain Chalmers set about starting
the pilot of Effective Care in Pregnancy and
Childbirth, the first area of clinical practice
reviewing RCT’s.
 This review exposed gaps in care between
research and clinical practice. This led to
belief in the benefits of evidence based
practice.
 Corticosteroid treatment reduced the
odds of babies dying from
complications of immaturity by 30 to
50%.
 But due to lack of the information
getting to the doctors, thousands died
because the 1972 study was not well
known. It took 17 years to spread the
knowledge.
 Meta-analysis of these studies helped
the use of steroids become a standard.
The Cochrane Collaboration
 http:// www.cochrane.org
 The success of “Effective Care in Pregnancy and
Childbirth” led to an international collaboration
being established.
 The UK National Health Service established the
Cochrane Center in Oxford.
 This center publishes systematic reviews of
RCT’s electronically in the Cochrane Database of
Systematic Reviews.
 Many countries can access this for free. In the
USA, we can get the abstracts for free.
Clinical Decision Making
 What test is the best to explore the
condition the patient presents with?
 Which treatment would be the most
effective?
 What diagnosis is indicated?
 The practitioner’s knowledge base,
skills, attitudes, resources, patient’s
expectations and concerns all feed into
the decision.
Increasing Clinical Knowledge, through
evidence based methods.
A definition from David Sackett,
McMaster University, Ontario , Canada:
Evidence Based Medicine: integrating
individual clinical expertise with the
best available external clinical evidence
from systematic research to achieve the
best possible patient management.
Dave Sackett
1990: Sackett’s “Just in Time” learning
An EBM Approach to Education
 Evidence cart on ward rounds - 1995
 Looked up 2-3 questions per patient
 Took 15-90 seconds to find
 1/3 changed treatment
 Rounds took longer!
Evidence Based Medicine
or Evidence Based Practice
Using the term Evidence Based Practice
is more inclusive of different areas of
health care practice.
The term practice encompasses more
than just physiological, anatomical or
biochemical processes found in
medicine.
Practices covers outcomes of clinical
activities that are greater than just
medicine.
Using Evidence Based Practice
Acknowledge that there are
uncertainties in clinical knowledge.
Both in self knowledge and in changes
to knowledge from new findings.
2. Use research information to reduce
uncertainties.
3. Know which information found is
strong and which is weak.
4. Determine probabilities of
uncertainties.
1.
New clinical skills in using EBP
1. Efficient literature searching.
2. Application of formal rules of evidence
in evaluating the clinical literature.
What skills are you currently using
to answer clinical questions?
 Attending seminars and conferences
 Reading journals
 Information from pharmaceutical
representatives
 Textbooks
 Published clinical guidelines
 Electronic searching
 Small group learning
 Talking to other colleagues
What is the average number of clinical
questions?
 Physicians report 2 questions for every 3
patients.
 Observation shows usually 5 questions for
each patient.
 Only 30% of questions were answered, usually
by asking a colleague.
 Textbooks were thought to be too old, lack of
time to find answers, and lack of knowledge
of where to look were given as reasons for not
finding answers.
Back to the cart
David Sackett in 1998, with his evidence cart
reported that with 71 information searches to
answer clinical questions, 52% confirmed the
management decision, 25% led to a new
therapy or treatment plan, 23% corrected a
previous plan.
S. Crowley in 2003, with CAR study showed
that 520 clinical questions when the answers
were sought in medical literature 53%
confirmed the patient management, 47% the
medication, diagnostic, or prognostic
information was changed.
The Study Data of 145 cases and clinical
decisions
 31 could be supported by a randomized



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controlled trial.
65 were supported by a head to head trial (not
a placebo-controlled trial).
23 were supported by case-control or cohort
studies.
4 were supported by case series reports.
22 could not be supported by a literature
study.
Optometric Application of EBP
“Whither Goes Evidence-Based
Optometry”
In the April 2009 issue of Optometry
and Vision Science, Editor Anthony
Adams makes his case for the use of
Evidence Based Optometry to find the
best research and utilize the research to
diagnose and provide therapy.
What happens when there is no
evidence?
Behavior Optometry: from Wikipedia
Is an expanded area of optometric practice that
claims to use a “holistic” approach to the
treatment of vision and vision information
processing problems.
The practice of behavior optometry
incorporates various vision therapy methods
and has been characterized a a complementary
alternative medicine practice.
A review in 2000 concluded that there were
insufficient controlled studies of the approach
and a 2008 review concluded that “ a large
majority of behavioural management
approaches are not evidence-based, and thus
cannot be advocated.”
from 2008 review by:
Brendan Barrett, “ a critical evaluation of the
evidence supporting the practice of
behavioural vision therapy” Ophthalmic and
Physiologic Optics 29
Oklahoma Academy Fall meeting
 Dr. Susan Crotty speaking on Evidence
Based prescribing for children and treatment
of amblyopia.
 NIH funded research on treatment options for
amblyopia
AOA
 Plans are in place to change Clinical
Guidelines to an Evidence Based Web
site much like the ADA page. This will
have all clinical guidelines in EB form,
hopefully in 2 years.
 New questions will be constantly
researched
 Eventually the practitioner may post
their own questions for research.
It all begins with a question.
Steps to EBP
Formulate Clinical Questions
Search for Evidence
Appraisal of research
Apply to clinical problem
Step 1
Formulate an answerable clinical
question
 Structure of researchable questions –
PICO
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Population/Patients
Intervention
Comparison
Outcome
Patients/Population
Identify the patient /population
characteristics that will affect your
question.
Intervention
Is there a treatment/therapy you are
considering or want to know more
about?
Comparison
Do you want a comparison between
two therapies?
Outcome
Are you or the patient wanting to know
the outcome of the disease or the
treatment options?
PICO: This question structure represents
epidemiological study design
Patient or Population
Intervention
or
comparison
outcome
Type of questions asked will lead to the type of
study that will answer the question.
Diagnosis
How to select and interpret
diagnostic tests.
Therapy
How to select treatments to
offer patients that do more
good than harm and that are
worth the efforts and costs of
using them.
Prognosis
How to estimate the patient’s
clinical course and
complications.
Harm/Etiology
How to identify causes for
disease.
Meta-Analysis
Systematic Review
Randomized Controlled Trial
Evidence
pyramid
Cohort Studies
Case Control Studies
Case Series/ Case Reports
Animal Research/ Laboratory Studies
Evidence Pyramid
Information usually starts with an idea
or laboratory research. The ideas turn
into drugs or tools that are tested in
labs, in animals, and finally in humans.
The human testing may go to clinical
trials.
As you move up the pyramid the
amount of available literature
decreases, but increases in its relevance
to the clinical setting.
New Terms from EBP
Meta-analysis: examines a number of
valid studies on a topic and combines
the results using accepted statistical
methodology as if they were from one
large study. This not only uses
information from RCTs, but also
appraises their validity.
Systematic Reviews: focus on clinical
topic and answer a specific question.
An extensive literature search is
conducted to identify all studies with
sound methodology. The studies are
reviewed, assessed and results
summarized. The Cochrane
Collaboration has done many studies
for systematic review topics and
includes 144 on vision and eye.
When meta-analysis or systemic review
is done, the value of the information
increases.
Type of question asked leads to study
design with best answer.
Type of question
Best type of study
Therapy
RCT>Cohort>Case
Control>Case series
Diagnosis
Prospective cohort, blind
comparison to a gold
standard
Risk factors
Cohort>Case
Control>Case series
Prognosis
Cohort>Case
Control>Case series
Prevention
RCT>Cohort>Case
Control>Case series
Clinical Exam
Prospective cohort, blind
comparison to a gold
standard
Cost
Economic analysis
What are your clinical questions?
Your 59 year old black patient is concerned
that he might have glaucoma. His older sister
had glaucoma and went blind. Your patient
wants to know:
Could he have glaucoma and will he go blind
like his sister?
Types of questions: glaucoma
What are the risk factors for glaucoma?
Etiology question.
Answer found in: Cohort Study
Will I go blind? Prognosis question.
Answer found in Prospective
Cohort Study
How should this patient be treated?
Eye drops, laser, surgery?
Intervention question.
Answer found in
Randomised Trial
You asked a question, now step 2.
Searching: how to find good
answers?
Should I ask a colleague?
12 occupational therapy questions
E.g., Is a 38-year old sewage worker
subject to a higher risk of contracting
Hepatitis A as a result of occupational
exposure? (No)
Obtain advice from 2 professionals on 3
cases each.
37% wrong answers
17% wrong if based on literature
65% wrong if not
Searching made easy 
3.
You found some answers are they valid?
Rapid Critical Appraisal
It’s peer-reviewed, therefore it must be OK?
Step 3: Appraise the evidence
Did you find good quality studies?
Two steps.
Did you ask good questions?
PICO
Was the research valid?
RAMMbo
What makes a good study?
 Lack of Bias and confounding
 Internal validity in the design,
randomization, blinding, accuracy in
testing and reporting.
 External validity in translating to the
real world.
Is there internal validity?
 Was the assignment of patients to treatment

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randomized.
Were all the patients who entered the trial
properly accounted for at its conclusion? Good
follow-up?
Were patients analyzed in groups to which
they were assigned?
Were patients, clinicians and study personnel
blinded?
Were the groups similar at the start of the
trial?
Were the groups treated equally?
What are the results?
 Were results correctly analyzed and do
you understand the results?
Is there external validity?
Do the results apply to your patient and
the population they represent?
Check population characteristics such
as: age, sex.
RAMMbo : Critical Appraisal Technique
R: Recruitment were the subjects representative of the
population?
A: Was the treatment allocation concealed before
randomization and were the groups comparable at
the start of the trial?
M: Was the comparable status of the study groups
maintained through equal management and
adequate follow up?
M: Measurement, were the outcomes measured with:
bo: blinded subjects and assessors and/or objective
outcomes?
The components of RAMMbo should
match up with the components of PICO.
Appraisal of Tests: RAMMbo
was the evaluation fair?
Population
Index test
Outcome
Measures
(Gold Standard)
Maintained?
Outcome
Measures
Representation?
(Gold Standard)
Comparator Test
Blinded or
Objective?
Step 4: Applying to the individual
 What do the results mean on average?
 What do they mean for this individual?
What are the alternatives to EBM?
A dilemma
You are very ill …
Which doctor do you want?
William Osler, 1900
Smart young doctor
Life long learning
The hardest conviction to get into the
mind of a beginner is that the education
upon which he is engaged is not … a
medical course, but a life course, for
which the work of a few years under
teachers is but a preparation.
Sir William Osler (1849-1919), from: The
Student of Medicine
What is evidence-based medicine?
Evidence-based medicine is the
integration of best research evidence
with clinical expertise and patient
values”
- Dave Sackett
Patient
Concerns
EBM
Best research Clinical
Expertise
evidence
Pros and cons of EBP
EBP is a new name for an
old practice. Literature
has always guided
clinical care.
EBP uses processes and
filters so that the
decisions are made on
strong evidence
EBP is cook book.
Decisions are solely made
on evidence, down
playing sound clinical
judgment.
The use of evidence is
one part of the process.
Decisions are blended
with individual clinical
expertise, patient
preference, and good
evidence.
EBP is mindless
application of
population information
to the treatment of one
person.
The last step in EBP is
to decide whether or
not the information
and results apply to the
patient.
Often there is not RCT
or gold standard to
address the clinical
question
Use the evidence
pyramid and look for
the next best level of
evidence. Sometimes
there is no evidence.
There can be difficulty
in getting access to the
evidence and in
conducting effective
searches to identify the
best evidence.
Librarians can help
identify the best
resources and teach
clinicians effective
searching skills
When can evidence based practice hurt
the patient?
 Poorly formed questions can lead to

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misdirection.
Wrong diagnosis or questions researched,
more clinical knowledge needed.
Lack of explaining treatment, therapy to
patient.
Poor communication to patient.
Rigidity in use of one arm of EBP.
Use by insurers or providers in preventing
care.
Where can you start?
 Librarian Martin will review sources.
 At Hasting Hospital: Up-to-date. Use
Resource tab and scroll down to up to date
link.