EBM --- Journal Reading Presenter ：林禹君 Date ： 2005/10/26

Users’ Guides to the Medical Literature Ⅱ. How to Use an Article About Therapy or Prevention B. What Were the Results and Will They Help Me in Caring for My Patients ？ Gordon H. Guyatt, MD. MSc; David L. Sackett, MD. MSc; Deborah J. Cook, MD. MSc; for the Evidence-Based Medicine Working Group

Clinical scenario 65 y/o male Brief history –Controlled HTN –6 months arterial fibrillation, resistant to cardioversion –No evidence for valvular or coronary heart disease long-term anticoagulants: –Benefit (reduce embolic stroke) v.s risk (hemorrhage)

The PICO P: non valvular arterial fibrillation I: warfarin C: warfarin and control treatment O: risk of embolism and complications of anticoagulation

The Search GRATEFUL MED MeSH: –Arterial fibrillation, warfarin, Stroke(explode cerebrovascular disorders Limit –English language, randomized controlled trial 9 articles –3: editorials, commentaries –1: prognosis –1: quality of life  The most recent of the 4  Warfarin in the prevention of stroke associated with nonrheumatic arterial fibrillation, NEJM. 1992

What were the results ？ How large was the treatment effect ？ How precise was the estimate of the treatment effect ？

What were the results ? How large was the treatment effect? –Absolute risk reduction –Relative risk –Relative risk reduction(RRR) How precise was the estimate of treatment effect? –Point estimate –95% confidence interval: true 95% of the time

When is the sample size big enough? The larger the sample size, the greater of our confidence Positive study  lower boundary of the CI, still clinically significant? Negative study  upper boundary of the CI, be important Other criteria for CI

What can the clinician do if the CI around the RRR is not reported in the article P-value –0.05: lower bound of 95% CI for RRR= 0 Cannot exclude  treatment had no effect – 0 +/- standard error*2 Calculate CI yourself or someone else

Will the results help me in caring for my patients ？ Can the results be applied to my patient care ？ Were all clinically important outcomes considered ？ Are the likely treatment benefits worth the potential harms and costs ？

Will the results help me in caring for my patients ? Can the results be applied to my patient care? –Inclusion/exclusion criteria –Whether there is some compelling reason why the results should “not” be applied to the p’t –Believable subgroup data: if difference is Large Very unlikely to occur by chance Results from analysis specified as a hypothesis before the study began One of only a very few subgroup analyses that were carried out Replicated in other studies

Were all clinically important outcomes considered? –Treatment improve outcomes that are “important” to patients –Substituted end point v.s important outcome Antiarrhythmic agent: abnormal ventricular depolarization  v.s life-threatening arrhythmia  –No deleterious effects on other outcomes Surgical trial  immediate and early mortality

Are the likely treatment benefits worth the potential harm and costs? –Number needed to treat (NNT)  before deciding on treatment, we must consider our patient’s risk of the adverse event if left untreated

Resolution of the scenario ( )

Conclusion Define the problem clearly Search: best available evidence Assess the quality of evidence Result Important Outcome Benefit/risk/cost

Thanks For Your Attention !!