www.cebm.net evidence-based practice for clinical years carl heneghan bm, bch ma, mrcgp, dphil...
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Evidence-Based Practice for Clinical Years
Carl Heneghan BM, Bch MA, MRCGP , DPhil
Clinical Lecturer, University of Oxford
Deputy Director CEBM
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Outline of the EBM Thread
• 9-9.10 Assignment • 9.10-9.30 Question formulation • 9.30-11.0 Critical appraisal of trials and SRs
• 11.0-11.30 Finding the evidence quickly
• Mon pm Tues am Preparation of CATs
• 3.30-5.00 Small group presentations (see back of workbook)
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Assignment
• Assigned to work in pairs • 7 minute presentation• 3 minutes for questions
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Assignment (criteria)
• Turning up
• Clinical Question • Search strategy• Appraisal• Interpretation of findings• Clear recommendation
• Overall Impression
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Atrial fibrillation and Warfarin
- a critically appraised topic example
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The Question
Mr. X is a 76 year old man who, on examination by his GP was found to have an irregularly irregular pulse.
An ECG then confirmed this man was in atrial fibrillation.
The GP then needed to decide whether this man should be put on Warfarin to reduce his risk of a stroke or whether aspirin would be sufficient.
P Man in atrial fibrillation- no previous history of a stroke
I Warfarin therapy
C Aspirin
O Reduced risk of a stroke
www.cebm.netThe Search
• PubMed: Clinical Queries (with therapy filters)• Atrial fibrillation AND warfarin → 145 papers• Atrial fibrillation AND warfarin AND aspirin AND stroke →
35 papers
BAFTA trial selected → randomised controlled trial
→ correct population (75+ years)
→ large sample size (973 patients)
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The Study appraisal Warfarin versus aspirin for stroke prevention in an elderly community population with atrial
fibrillation (the Birmingham Atrial Fibrillation Treatment of the Aged Study, BAFTA): a randomised controlled trial.
J Mant, FDR Hobbs, K Fletcher et al (2007), Lancet, 307:493-503
• 973 patients over the age of 75• Randomisation- stratified by age and sex in to 6 groups (75-79, 80- 84, 85+)
- randomly allocated to a treatment when GP telephoned- good balance achieved → 488 warfarin, 485 aspirin
• Aspirin cohort – 75mg daily• Warfarin cohort- target INR = 2.5 (2-3 acceptable)
• Ascertainment- patients were reviewed by their GP every 6 months- yearly postal questionnaires were sent- mean follow-up time = 2.7 years (sd = 1.2)
• Primary outcome → first occurrence of fatal or disabling stroke• Secondary outcome → major extracranial haemorrhage
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Results interpretation of findings
• There were fewer primary events in people assigned to warfarin then in people assigned to aspirin:
Warfarin: 24 events → 1.8% per year Aspirin: 48 events → 3.8% per year
Relative risk = 0.48 (95%CI = 0.28-0.80)
• No increased risk of haemorrhage in those on warfarin than in those on aspirin:
Relative risk = 0.88 (95%CI = 0.46-1.63)
• This was shown to be true for all the subgroups.
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The Implications
• These results suggest that Mr. X should be put on warfarin, provided he has no other contraindications.
• This study suggests that warfarin will be more effective than aspirin in reducing his risk of a stroke.
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Title
Names
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The Question
Mr. X.P
I
C
O
www.cebm.netThe Search
• We searched
• We selected
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The Study appraisal Study title
• Critical appraisal
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The Results (interpretation of findings)
• There were
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The Implications
• These results suggest
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: Asking well-formulated questions
www.cebm.netAngela is a patient on the medical ward who recently moved to the area to be closer to her son and his family.
She is 72 years old and has a history of congestive heart failure. She was admitted 2 days ago having presenting with non specific chest pain and has been diagnosed with a Non –ST elevation MI.
She has been hospitalized twice within the last 6 months for worsening of heart failure.
At the present time she says she is pain free remains and is extremely diligent about taking her medications (lisinopril and aspirin) and wants desperately to stay out of the hospital. She reports being mobile and lives alone with several cats.
She also tells you she is a bit hard of hearing, has a slight cough, is a smoker of 20 cigs a day for 40 years. When you examine her: BP is 170/90, her ankles are slightly swollen and her pulse is 80 and irregularly irregular.
What are your
questions?
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Background Questions
• About the disorder, test, treatment, etc.
• 2 components:
a. Root* + Verb: “What causes …”
b. Condition: “… SARS?”
• * Who, What, Where, When, Why, How
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Background & Foreground
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Foreground Questions
• About patient care decisions and actions
4 (or 3) components:
a. Patient, problem, or population
b. Intervention, exposure, or maneuver
c. Comparison (if relevant)
d. Clinical Outcomes (including time horizon)
www.cebm.netPatient or Problem
Intervention Comparison intervention
Outcomes
Tips for Building
Describe a group of patients similar to your own
What intervention are you considering
What is the main alternative to the intervention
What do you hope to accomplish with the intervention
Example
“In elderly patients with congestive heart failure …
…does treatment with spirinolactone…
…when compared with standard therapy alone…
…lead to a decrease in hospitalization ”
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Scenario 2 – Beta blockers in heart failure?Over afternoon tea you are discussing a patient with heart failure who had a MI about 6 weeks ago . He had recovered well though : no breathlessness, pulse 80 reg, BP 136/85, chest is clear, but echocardiography shows reduced function with an LVEF of 30%. You wonder whether beta-blockers are safe and helpful in such a patient
PICO
www.cebm.netStockings for long haul flights?
A 43 year old male asked for a repeat prescription and wanted advice about preventing deep vein thrombosis on a 12 hour flight (his brother had a DVT last year) You suggest stockings as the most effective prevention
PICO
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Your Clinical Questions
•Write down one recent patient problem
•What is the PICO of the problem?