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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
Outline of the EBM Thread Assignment Question formulation Critical appraisal of trials and SRs Finding the evidence quickly Mon pm Tues amPreparation of CATs Small group presentations (see back of workbook)
Assignment Assigned to work in pairs 7 minute presentation 3 minutes for questions
Assignment (criteria) Turning up Clinical Question Search strategy Appraisal Interpretation of findings Clear recommendation Overall Impression
Atrial fibrillation and Warfarin - a critically appraised topic example
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
The 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)
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: patients over the age of 75 Randomisation- stratified by age and sex in to 6 groups (75-79, , 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
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 = ) No increased risk of haemorrhage in those on warfarin than in those on aspirin: Relative risk = 0.88 (95%CI = ) This was shown to be true for all the subgroups.
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.
The Question Mr. X. P I C O
The Search We searched We selected
The Study appraisal Study title Critical appraisal
The Results (interpretation of findings) There were
The Implications These results suggest
: Asking well-formulated questions
Angela 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?
Background Questions About the disorder, test, treatment, etc. 2 components: a. Root* + Verb: What causes … b. Condition: … SARS? * Who, What, Where, When, Why, How
Background & Foreground
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)
Patient or Problem InterventionComparison intervention Outcomes Tips for Buildi ng 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 Exam ple In elderly patients with congestive heart failure … …does treatment with spirinolactone … …when compared with standard therapy alone… …lead to a decrease in hospitalization
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 PICOPICO
Stockings 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 P I C O
Your Clinical Questions Write down one recent patient problem What is the PICO of the problem?