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

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ebm and e b guidelines
EBM and E-B Guidelines
  • EBM integrates evidence, expertise, and the unique biology and values of individual patients.
  • Local EB Provision ought to integrate evidence, expertise, and the unique biology and values of the local scene.
ebm and e b guidelines2
EBM and E-B Guidelines
  • 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
ebm and e b guidelines3
EBM and E-B Guidelines
  • 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
1 burden
1. Burden
  • The burden of illness, disability, and untimely death that would occur if the evidence were NOT applied
  • the consequences of doing nothing
2 barriers
2. Barriers
  • Patient-values & preferences
  • Geography
  • Economics
  • Administration/Organisation
  • Tradition
  • “Expert” opinion
3 behaviours
3. Behaviours
  • The behaviours required from providers and patients if the evidence is applied.
  • All that guidelines can do is specify the former!
4 balance
4. Balance
  • The opportunity cost of applying this guideline rather than some other one.
killer b s
Killer B’s
  • Burden: too small to warrant action.
  • Barriers: ultimately down to patients’ values.
  • Behaviours: may not be achievable.
  • Balance: may favour another guideline over this one.
two monumental wastes of time and energy
Two monumental wastes of time and energy
  • First, national/international evidence-summarising groups prescribing how patients everywhere should be treated.
  • Their expertise: predicting the health consequences if you do treat.
  • Their ignorance: the local B’s, and whether killer B’s are operating.
two monumental wastes of time and energy10
Two monumental wastes of time and energy
  • Second, local groups attempting to systematically review the evidence.
  • Their expertise: identifying the local B’s and eliminating the killer B’s
  • Their ignorance: searching for all relevant evidence; Chinese; performing tests for heterogeneity.
applying a study result to my patient
Applying a study result to my patient
  • Never interested in “generalising”
  • Am interested in a special form of extrapolation: particularising
extrapolating particularising to my individual patient
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?
  • if no contribution, I restart my search
  • if it could help, I need to integrate the evidence with my clinical expertise and my patient’s unique biology and values...
to add clinical expertise and patient s biology values
To add Clinical Expertise and Patient’s Biology & Values:
  • 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?
  • What is the treatment’s FEASIBILITY in my practice/setting?
  • What are my patient’s VALUES ?
to add clinical expertise and patient s biology values14
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:
  • The report gives me (or I can calculate) an Absolute Risk Reduction [ARR] for the average patient in the trial.
  • ARR = probability that Rx will help the average patient.
for example warfarin in nonvalvular atrial fibrillation
For example, Warfarin in nonvalvular atrial fibrillation:

After 1.8 years of follow-up in an RCT:

  • Control Event Rate (placebo) = 4.3%
  • Exper. Event Rate (warfarin) = 0.9%
  • 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
how can i adjust that arr for my pt s risk and responsiveness
How can I adjust that ARR for my pt’s Risk and Responsiveness?
  • 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
  • Clinicians are not very accurate at estimating absolute Risk and Responsiveness
how can i adjust that arr for my pt s risk and responsiveness17
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
  • So, I express them as decimal fractions:
    • 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)
how can i adjust that arr for my pt s risk and responsiveness18
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
  • If ARR is 3.4%
  • and I judge that their f~risk is 3
  • and that their f~resp is 0.5
  • then the probability that warfarin will help my patient = 3.4% x 3 x 0.5 = 5.1%
must also consider the probability that i will do harm
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.
  • Absolute Risk Increase = 3% at 1 yr, so ARI estimated to be 5% in 1.8 years ACPJC 1994;120:52
and adjust the probability of harm for my patient
…and adjust the probability of harm for my patient
  • Again, can express my clinical judgement in relative terms: f~harm
  • Given my patient’s age, I judge their f~harm to be doubled: 2
  • then the probability that Rx will harm my patient = ARI x f~harm = 5% x 2 = 10%
can now begin to estimate the likelihood of help vs harm
Can now begin to estimate the Likelihood of Help vs. Harm
  • Probability of help: ARR (embolus) x f~risk x f~resp = 5.1%
  • Probability of harm: ARI (haemorrhage) x f~harm = 10%
  • My patient’s Likelihood of Being Helped vs. Harmed [LHH] is: (5.1% to 10%) or 2 to 1 against warfarin!
  • …or is it ?
the lhh has to include my patient s values
The LHH has to include my patient’s values
  • 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
  • Expressed in relative terms = s~
    • if the bleed is half as bad as the embolus, then s~ = 0.5
on in patient services in oxford and toronto
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):
  • for most of her patients, a bleed is only 1/5th as bad as a stroke
  • so the s~ is 0.2
so the lhh becomes
So the LHH becomes:
  • {ARR for embolus} x {f~risk} x {f~resp} vs. {ARI for bleed} x {f-harm} x {s~}
  • 3.4% x 3 x 0.5 = 5.1% vs. 5% x 2 x 0.2 = 2%
  • LHH = 5.1 to 2 or 2.5 to1
    • (I am more than twice as likely to help than harm my patient if they accept my offer of Rx)
we can work out the lhh for most patients 6 minutes
We can work out the LHH for most patients <6 minutes
  • To be feasible on our service: has to be “do-able” in 3 minutes.
reactions from our patients
Reactions from our patients
  • All are grateful that their values/opinions are being sought
  • »1/3 want to see the calculations, perhaps change their value for s~, and make up their own minds.
  • »1/3 adopt the LHH as presented.
  • »1/3 say “Whatever you tell me, doctor!”