EVIDENCE BASED MEDICINE for Beginners

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EVIDENCE BASED MEDICINEfor Beginners

• Maria Fidelis Manalo, MD, Msc Epidemiology
• Department of Community Family Medicine
• FEU-NRMF Medical Center
• Philippines

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Evidence-Based Medicine Definition

• the conscientious, explicit and judicious use of
  current best evidence in making decisions about
  the care of the individual patient
  
• David Sackett

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EBMHistorical Evolution

• Has roots going back to 19th c. 
• Recently broadened interest due to information
  explosion that increased dramatically in the last
  decade.
• Has become more formalized that have enabled
  practitioners to approach medical problems and
  evaluate medical literature with greater
  consistency and to deal with massive amounts of
  medical information via a qualitative approach.

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EBMUsefulness

• Instead of routinely reviewing the contents of
  dozens of journals for interesting articles, EBM
  suggests that you target your reading to issues
  related to specific patient problems as
  encountered. 
• This makes EBM a life-long self-directed and
  problem-based learning process.

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Misapprehensions Misinterpretations about EBM

• 1) Evidence-based medicine ignores clinical
  experience and clinical intuition.
• 2) Understanding of basic investigation and
  pathophysiology plays no part in evidence-based
  medicine.
• 3) Evidence-based medicine ignores standard
  aspects of clinical training such as the physical
  examination.

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Types of Questions
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(1) Background Questions

• Asked for general knowledge about a disorder 
• Has two essentials components
• a question root ( who, what, where, how, why)
  with a verb
• a disorder

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Background Questions

• Textbooks answer background questions, they
  contain collected synthesized wisdom for topics
  that do not change often. 
• Not all topics are covered, easy to use,
  relatively inexpensive and can be opinion-based
  rather than evidence-based, written by experts in
  their fields.

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(2) Foreground Questions

• Asked for specific knowledge about managing
  patients with a disorder
• It has 4 components (PICO analysis)
• P - Patient/Population
• I - Intervention
• C - Comparison
• O - Outcome
•  

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• Basis of Evidence-based care involves the
  integration of the best research evidence with
  clinical expertise and patient values.            
  

Best Clinical Evidence
Patients Needs/ Preferences
Clinical Experience
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Foreground Information
Background Information

• Novice Expert
  Searcher   Searcher
• At all stages you ask both kinds of questions,
  but as experience increases the foreground
  questions increase. 
• It is essential that you understand the
  background question before attempting to answer
  the foreground ones.
•  

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EBM Principles

• 1.  Construct a well-built clinical question
• and classify it into one category (therapy,
• diagnosis, etiology or prognosis)
• 2.  Find the evidence in health care literature
• 3.  Critically appraise or formally evaluate
• for validity and usefulness
• 4.  Integrate the evidence with patient
• factors to carry out the decision
• 5.  Evaluate the whole process

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PICO ANALYSIS

• Before attempting to search for the evidence in
  the literature, construct a well-built or clearly
  structured question that could be broken into the
  following four parts

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(1) Patient /Population

• What is the primary problem, disease or
  co-existing conditions? 
• On what groups do you want information?  
• How would you describe a group of patients
  similar to the one in question?  
• Sometimes age or sex of a patient may be relevant
  and should be included. 
• Example post-menopausal women with hypertension

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(2) Intervention

• What medical event do you want to study the
  effect of?  
• Which main intervention are you considering,
  prescribing a drug, ordering a test, ordering
  surgery?. . . .
• Example ERT

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(3) Comparison

• Compared to what?  
• Better or worse than no intervention at all or
  than another intervention?  
• What is the main alternative to compare with the
  intervention, are you trying to decide between
  two drugs, a drug and a placebo, or two
  diagnostic tests? 
• Sometimes there is no comparison.  
• - Example no ERT

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(4) Outcome

• What is the effect of the intervention? 
• What do you hope to accomplish, measure, improve,
  or affect with this intervention? 
• What are you trying to do for the patient,
  relieve or eliminate the symptoms, reduce side
  effects, reduce cost? .. .
• Example improve quality of life

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What makes a clinical question well built?

• Question should be directly relevant to the
  problem at hand.
• Question should be phrased to facilitate
  searching for a precise answer.
• Asking a well-built question, like many clinical
  skills, needs practice.

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Categories of EBM Questions

• After constructing the PICO analysis, determine
  the category of the question. 
• There are the four categories of EBM questions

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1) Therapy

• Solves questions about which treatment to
  administer, and what might be the outcome of
  different treatment options. 
• For most therapy questions one may want to look
  for the best evidence namely a randomized
  controlled study, and if the study can be a
  double blind, so much the better. 
• - Example find the evidence for the use of
• anticoagulants in patients with atrial
  fibrillation

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2) Diagnosis

• Solves questions about degree to which a test is
  reliable and clinically useful, to decide whether
  the patient would benefit from it
• Most articles compare result of a certain
  diagnostic test with that of a standard test
  regarded as being a "gold standard". 
• - Example search for the best diagnostic
  test for
• Alzheimer's disease  

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3) Etiology

• Solves problems about the relationship between a
  disease and a possible cause
• - Example find out if a diet rich in
  saturated fats
• increases the risk of heart disease, and if
  so by
• how much

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4) Prognosis

• Answers questions about a patient's future
  health, life span and quality of life in the
  event one chooses a particular treatment option
• - Example find how would the quality of life
  change for a patient who undergoes surgery for
  prostate cancer 
• The next step would be to determine the best
  study design needed to answer the clinical
  question.

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Types of Research Studies

• Certain study designs are superior to others when
  answering particular questions.
• RCT are considered the best for addressing
  questions about therapy.
• Etiology questions may be addressed by
  case-control cohort studies. 
• Other aspects relevant to study design include
  placebo comparison group and follow-up.

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1) Randomized Controlled Trial (RCT)

• Answers therapy, prevention questions
• Randomization avoids selection bias

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2) Cohort study

• Answers prognosis, etiology, prevention questions
• Cohorts are defined populations that, as a whole,
  are followed in an attempt to determine
  distinguishing subgroup characteristics.  
• Researchers identify and compare two groups over
  a period of time. 

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2) Cohort study

• At the start of the study, one of the groups has
  a particular condition or receives a particular
  treatment, and the other does not. 
• At the end of a certain amount of time,
  researchers compare the two groups to see how
  they did. 

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3) Case Control study

• Answers prognosis, etiology, prevention questions
• Identifies patients who already have the outcome
  of interest and control patients without that
  outcome, and look back to see if they had the
  exposure of interest or not.  

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4) Case series Case Reports 

• Answers prognosis, etiology, prevention
  questions
• Consist either of collections of reports on the
  treatment of individual patients, or of reports
  on a single patient.