how do you practise evidence-based medicine?

How does one do all of this?
A clinician practicing EBM would ideally follow a series of steps to get to the evidence needed to make decisions on the course(s)of treatment for his patients.  As the practice of EBM usually starts and ends with a patient.

These steps are outlined in Table 1

Table 1: Steps in the practice of Evidence-Based Medicine

1. Form answerable clinical questions

2. Search for the best external evidence

3. Critically appraise the evidence for validity and importance

4. Apply the evidence in clinical practice

5. Evaluate his performance as a practitioner of EBM

There are eight different kinds of questions which can be asked as is outlined in Table 2.

In order for both the patient and the clinician to benefit, the questions you ask a patient should be well built. Which means  that they should be directly relevant to the patient being treated.  Also try to phrase the questions in such a way that they direct your search for information to the relevant answers.   The elements of well-constructed clinical questions are summarized in Table 3.

Table 2: The central tasks of clinical work or where clinical questions
may arise from.

  1. Clinical findings: How to properly gather and interpret findings from patient history and physical examination.
  1. Etiology: how to identify causes for disease (including its iatrogenic forms
  1. Differential diagnosis: When considering the possible causes of a patientís clinical problem, how  to rank them by likelihood, seriousness and treatability.
  1. Diagnostic test: how to select and interpret diagnostic tests, in order to confirm or exclude a diagnosis based on considering their precision, accuracy, acceptability, expense, safety etc
  1. Prognosis: How to estimate the patientís likely clinical course over time and anticipate  likely complications of the disease.
  1. Therapy: how to select treatment to offer patients that do more good than harm and that are worth the efforts and costs of using them
  1. Prevention: how to reduce the chance of disease by identifying and modifying risk factors and how to diagnose disease early by screening.
  1. Self-improvement: How to keep up to date, improve your clinical skills and run a better, more efficient clinical practice.

Table 3:  The four elements of well-built clinical questions


Patients or problem

(a cause, a prognostic factor, a treatment, etc)

Comparison Intervention 
(if necessary)


Tips for Building

Starting with your patient, ask "How would I describe a group of patients similar to mine?" Balance precision with brevity

Ask "Which main intervention am I considering?" 
Be specific

Ask "What is the main alternative to compare with the intervention?" Again, be specific

Ask "What can I hope to accomplish?" or "What could this exposure really affect?" Again, be specific


"In patients with heart failure from dilated cardiomyopath y who are in sinus rhythm...."

"... would adding  anticoagulation with warfarin to standard heart failure therapy,..."

"when compared with standard therapy alone,..."

"..lead to lower mortality or morbidity from thromboembolis m Is this enough to be worth the increased risk of bleeding?"


The best way to explain this process is to illustrate it with an example.  For this purpose we look at the following case study:

Mr Evan Dince is a 40 year old male who has been recently diagnosed with HIV, his CD4 count is 275cells/mL. Although he is medically well, and has no complaints at present, he is anxious to start antiretroviral treatment. He asks you, his GP, for advice on the best time to start antiretroviral therapy. You decide to undertake a search of current best evidence to provide correct up-to-date information to your patient.

Module managing team:
Prof Jimmy Volmink

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