EBM and EB Guidelines EBM integrates evidence expertise

EBM and E-B Guidelines EBM integrates evidence, expertise, and the unique biology and values of individual patients. l Local EB Provision ought to integrate evidence, expertise, and the unique biology and values of the local scene. l Centre for Evidence-Based Medicine

EBM and E-B Guidelines l l The best evidence comes from systematic reviews (such as Cochrane) and/or E-B journals of 2º publication: » Much more likely (than personal search and critical appraisal) to be true » Saves the clinician’s precious (scarce!) time Avoids error and duplication of effort Centre for Evidence-Based Medicine

EBM and E-B Guidelines l l But NO systematic review can (or should try to) identify the “ 4 B’s: » Burden » Barriers » Behaviours » Balance They can ONLY be determined at the local (or even patient) level Centre for Evidence-Based Medicine

1. Burden The burden of illness, disability, and untimely death that would occur if the evidence were NOT applied l the consequences of doing nothing l Centre for Evidence-Based Medicine

2. Barriers Patient-values & preferences l Geography l Economics l Administration/Organisation l Tradition l “Expert” opinion l Centre for Evidence-Based Medicine

3. Behaviours The behaviours required from providers and patients if the evidence is applied. l All that guidelines can do is specify the former! l Centre for Evidence-Based Medicine

4. Balance l The opportunity cost of applying this guideline rather than some other one. Centre for Evidence-Based Medicine

Killer B’s Burden: too small to warrant action. l Barriers: ultimately down to patients’ values. l Behaviours: may not be achievable. l Balance: may favour another guideline over this one. l Centre for Evidence-Based Medicine

Two monumental wastes of time and energy First, national/international evidencesummarising groups prescribing how patients everywhere should be treated. l Their expertise: predicting the health consequences if you do treat. l Their ignorance: the local B’s, and whether killer B’s are operating. l Centre for Evidence-Based Medicine

Two monumental wastes of time and energy Second, local groups attempting to systematically review the evidence. l Their expertise: identifying the local B’s and eliminating the killer B’s l Their ignorance: searching for all relevant evidence; Chinese; performing tests for heterogeneity. l Centre for Evidence-Based Medicine

Applying a study result to my patient l Never interested in “generalising” l Am interested in a special form of extrapolation: particularising Centre for Evidence-Based Medicine

Extrapolating (particularising) to my individual patient: First and foremost: Is my patient so different from those in the trial that its results can make no contribution to my treatment decision? l if no contribution, I restart my search l if it could help, I need to integrate the evidence with my clinical expertise and my patient’s unique biology and values. . . l Centre for Evidence-Based Medicine

To add Clinical Expertise and Patient’s Biology & Values: l What is my patient’s RISK ? » of the event the treatment strives to prevent? » of the side-effect of treatment? What is my pt’s RESPONSIVENESS? l What is the treatment’s FEASIBILITY in my practice/setting? l What are my patient’s VALUES ? l Centre for Evidence-Based Medicine

To add Clinical Expertise and Patient’s Biology & Values: I begin by considering Risk and Responsiveness for the event I hope to prevent with the treatment: l The report gives me (or I can calculate) an Absolute Risk Reduction [ARR] for the average patient in the trial. l ARR = probability that Rx will help the average patient. l Centre for Evidence-Based Medicine

For example, Warfarin in nonvalvular atrial fibrillation: After 1. 8 years of follow-up in an RCT: l Control Event Rate (placebo) = 4. 3% l Exper. Event Rate (warfarin) = 0. 9% l so, for the average patient in the trial, the probability of being helped, or Absolute Risk Reduction = (CER - EER) = 3. 4% ACPJC 1993; 118: 42 Centre for Evidence-Based Medicine

How can I adjust that ARR for my pt’s Risk and Responsiveness? l Could try to do this in absolute terms: » my Patient’s Expected Event Rate: PEER » and multiply that by the RRR » and factor in my Patient’s expected responsiveness l Clinicians are not very accurate at estimating absolute Risk and Responsiveness Centre for Evidence-Based Medicine

How can I adjust that ARR for my pt’s Risk and Responsiveness? Clinicians are pretty good at estimating their patient’s relative Risk and Responsiveness l So, I express them as decimal fractions: l » f~risk (if at three times the risk, f~risk = 3) » f~resp (if only half as responsive [e. g. , low compliance], f~resp = 0. 5) Centre for Evidence-Based Medicine

How can I adjust that ARR for my pt’s Risk and Responsiveness? probability that Rx will help my patient = ARR x f~risk x f~resp l If ARR is 3. 4% l and I judge that their f~risk is 3 l and that their f~resp is 0. 5 l then the probability that warfarin will help my patient = 3. 4% x 3 x 0. 5 = 5. 1% l Centre for Evidence-Based Medicine

Must also consider the probability that I will do harm: In the case of warfarin: serious bleeding (requiring transfusion) from the g-i tract, or into the urine, soft tissues or oropharynx. l Absolute Risk Increase = 3% at 1 yr, so ARI estimated to be 5% in 1. 8 years l ACPJC 1994; 120: 52 Centre for Evidence-Based Medicine

…and adjust the probability of harm for my patient Again, can express my clinical judgement in relative terms: f~harm l Given my patient’s age, I judge their f~harm to be doubled: 2 l then the probability that Rx will harm my patient = ARI x f~harm = 5% x 2 = 10% l Centre for Evidence-Based Medicine

Can now begin to estimate the Likelihood of Help vs. Harm Probability of help: ARR (embolus) x f~risk x f~resp = 5. 1% l Probability of harm: ARI (haemorrhage) x f~harm = 10% l My patient’s Likelihood of Being Helped vs. Harmed [LHH] is: (5. 1% to 10%) or 2 to 1 against warfarin! l Evidence-Based …or is Medicine it ? Centre for l

The LHH has to include my patient’s values l I need to take into account my patient’s views (“preferences, ” “utilities”) about the relative severity: » of the bleed I might cause » to the embolus I hope to prevent l Expressed in relative terms = s~ » if the bleed is half as bad as the embolus, then s~ = 0. 5 Centre for Evidence-Based Medicine

On in-patient services in Oxford and Toronto: When Dr. Sharon Straus has described a typical embolic stroke (with its residual disability) and typical moderate bleed (brief hospitalisation and transfusion but no permanent disability): l for most of her patients, a bleed is only 1/5 th as bad as a stroke l so the s~ is 0. 2 l Centre for Evidence-Based Medicine

So the LHH becomes: l {ARR for embolus} x {f~risk} x {f~resp} vs. {ARI for bleed} x {f-harm} x {s~} l 3. 4% x 3 x 0. 5 = 5. 1% 5% x 2 x 0. 2 = 2% l LHH = 5. 1 to 2 or 2. 5 to 1 vs. » (I am more than twice as likely to help than harm my patient if they accept my offer of Rx) Centre for Evidence-Based Medicine

We can work out the LHH for most patients <6 minutes l To be feasible on our service: has to be “do-able” in 3 minutes. Centre for Evidence-Based Medicine

Reactions from our patients All are grateful that their values/opinions are being sought l » 1/3 want to see the calculations, perhaps change their value for s~, and make up their own minds. l » 1/3 adopt the LHH as presented. l » 1/3 say “Whatever you tell me, doctor!” l Centre for Evidence-Based Medicine