EVIDENCE BASED MEDICINE for Beginners Maria Fidelis Manalo, MD, Msc Epidemiology Department of Community & Family Medicine FEU-NRMF Medical Center Philippines

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

EBM Historical 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.

EBM Usefulness 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.

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.

Types of Questions

(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

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.

(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  

Best Clinical Evidence Basis of Evidence-based care involves the integration of the best research evidence with clinical expertise and patient values.             Best Clinical Evidence Patient’s Needs/ Preferences Clinical Experience

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.  

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

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

(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

(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

(3) Comparison Compared to what? 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. (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

(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

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.

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

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

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  

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

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.

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.

1) Randomized Controlled Trial (RCT) Answers therapy, prevention questions Randomization avoids selection bias

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. 

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. 

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.  

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.