ebm talk-general-mar99-ppt95
TRANSCRIPT
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Centre for Evidence-Based Medicine
Problemas
Necesitamos evidencia (sobre la presición de métodos diagnósticos, el poder de los marcadores pronósticos, la eficacia y la seguridad de las intervenciones, etc.) alrededor de 5 veces por cada paciente internado y tres veces por cada dos pacientes ambulatorios.
Sólo un tercio de las veces acudimos a la evidencia.
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Centre for Evidence-Based Medicine
Problemas:
Para mantenerse actualizado, sólo en Medicina interna, necesitamos leer 17 articulos diarios, los 365 días del año.
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Centre for Evidence-Based Medicine
Minutos por semana de lectura sobre los pacientes
Auto-Reportes sobre 17 ateneos: Estudiantes de Medicina: 90 minutes Residentes de Primer año: 0 (up to 70%=none) Residentes de otros años: 20 (up to 15%=none) Pasantes: 45 (up to 40%=none) Pasantes Seniors: 30 (up to 15%=none) Consultores:
» Grad. Post 1975: 45 (up to 30%=none)» Grad. Pre 1975: 30 (up to 40%=none)
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Centre for Evidence-Based Medicine
Deterioro de la performance también
Determinantes más importantes para tratar, o no, pacientes hipertensos:
1. Nivel de Tensión Arterial
2. Edad del Paciente
3. Año de Graduación del Médico
4. Grado de deterioro de órgano blanco
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Centre for Evidence-Based Medicine
Medicina Basada en la Evidencia es:
La práctica de la MBE es la integración de: Experiencia clínica individual con La mejor evidencia clinica disponible de
investaciones sistemáticas y Valores de los pacientes y expectativas
individuales
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Centre for Evidence-Based Medicine
I.Experiencia Clínica Individual
Habilidades clínicas y juicios clínicos Determinar si la evidencia (o guía)
aplica al paciente individual en su totalidad, y si es así, cómo
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Centre for Evidence-Based Medicine
II. Mejor Evidencia Externa:
De investigaciones clínicas en pacientes sanos
Tienen un tiempo de aplicación (10 años aproximadamente)
Reemplaza test diagnósticos aceptados y nuevos tratamientos con mayor poder, eficacia, efectividad y seguridad.
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Centre for Evidence-Based Medicine
III. Valores y Expectativas de los Pacientes
Siempre han jugado un rol central en determinar si, y cuáles, intervenciones tendrán lugar.
Mejoras en la integración de las preferencias y cuantificación de las mismas.
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Centre for Evidence-Based Medicine
Que no es la MBE:
La MBE no es una receta de cocina» La evidencia necesita extrapolar los
hallazgos a mis pacientes con sus particularidades biologicas únicas.
La MBE no es medicina de costo minimización o de recorte» Cuando la eficacia para mis pacientes es el
objetivo los costos pueden incluso aumentar, mas que disminuir.
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Centre for Evidence-Based Medicine
Medicina Basada en la Evidencia: la práctica.
Cuando el cuidado de pacientes crea la necesidad para la búsqueda de información:
1 Traducir la pregunta a una pregunta que pueda ser contexada (paciente-procedimiento-resultado).
2 Búsqueda eficiente de la mejor evidencia disponible » Literatura secundaria (, Cochrane; E-B Journals)» Literatura primaria
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Centre for Evidence-Based Medicine
Medicina Basada en la Evidencia: la práctica
3 Critical appraisal of the evidence for its validity and clinical applicability generation of a 1-page summary.
4 Integration of that critical appraisal with clinical expertise and the patient’s unique biology and beliefs action.
5 Evaluation of one’s performance.
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Centre for Evidence-Based Medicine
We needn’t always carry out all 5 steps to provide
E-B Care
Asking an answerable question. SearchingSearching for the best evidence. Critically-appraisingappraising the evidence. Integrating the evidence with our
expertise and our patient’s unique biology and values
evaluating our performance
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Centre for Evidence-Based Medicine
We’ve identified 3 different modes of practice
“Searching & appraising”» provides E-B care, but is expensive in time and
resources “Searching only”
» much, quicker, and if carried out among E-B resources, can provide E-B care
“Replicating” the practice of experts» quickest, but may not distinguish evidence-
based from ego-based recommendations
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Centre for Evidence-Based Medicine
Even fully EB-trained clinicians work in all 3
modes
“Searching & appraising” mode for the problems I encounter daily.
“Searching only” mode among E-B resources for problems I encounter once a month.
“Replicating” the practice of experts mode for problems I encounter once a decade(and crossing my fingers!).
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Centre for Evidence-Based Medicine
Patients can benefit
Even if <10% of clinicians are capable of practicing in the “searching & appraising” mode (5% of GPs)
As long as most of them practice in a “searching” mode within high-quality evidence sources (70-80% of GPs):» Cochrane Library, E-B Journals, E-B
Guidelines, etc
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Centre for Evidence-Based Medicine
Three solutions
Clinical performance can keep up to date:1 by learning how to practice evidence-
based medicine ourselves.2 by seeking and applying evidence-based
medical summaries generated by others.3 by applying evidence-based strategies
for changing our clinical behaviour.
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Centre for Evidence-Based Medicine
Information required within seconds
Systematic reviews, periodically updated, of randomised trials of the effects of health care (from all sources, and in all languages):
The Cochrane Collaboration.
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Cochrane Systematic Reviews (522; another 500 in preparation)
Database of Abstracts of Reviews of Effectiveness (1895)
Registry of Randomised Controlled Trials (218,355)
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Centre for Evidence-Based Medicine
Information required within seconds
CD-Evidence-based journals of 2º publication:
screen 50-70 clinical journals per week for clinical articles that pass critical appraisal quality filters conclusions likely to be true.
select the subset that are clinically relevant.
summarise as “more-informative” abstracts.
add commentaries from clinical experts.
introduce with declarative titles.
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Centre for Evidence-Based Medicine
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Centre for Evidence-Based Medicine
2. Seeking and Applying EBM generated by others
MBE esta publicado en: Inglés Francés Alemán Italiano Portugués Español
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Centre for Evidence-Based Medicine
2. Seeking and Applying EBM generated by others
New Evidence-based journals of 2º publication: E-B Cardiovascular Medicine E-B Health Policy & Management E-B Nursing E-B Mental Health
And as new departments in 1º journals.
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Centre for Evidence-Based Medicine
2. Seeking and Applying EBM generated by others
E-B Textbooks: E-B Pain Relief E-B Cardiology
includes icons for levels of evidence “E-B On-Call”
includes > 1300 CATs
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Centre for Evidence-Based Medicine
Can you really practice EBM?
Is there any “E” for EBM ?
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Centre for Evidence-Based Medicine
Conventional Wisdom
“only about 15% of medical interventions are supported by solid scientific evidence” (BMJ Editorial)
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Centre for Evidence-Based Medicine
Even on the U.S. Talk-Shows: (“Health Outrage of
the Week”)
“..... this would put 80 to 90 per cent of accepted medical procedures in this country under the heading of quackery!”
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Centre for Evidence-Based Medicine
Problems with Conventional Wisdom
uses clinical manoeuvres, rather than patients, as the denominator.
tends to focus on high-technology, “big ticket” items.
relies on simple literature searches that miss over half of the most rigorous types of evaluations.
conducted from armchairs.
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Centre for Evidence-Based Medicine
Performed an empirical study on a busy in-patient
service
on the general medicine in-patient service of the Nuffield Department of Medicine at the Oxford-Radcliffe NHS Hospital Trust (“The John Radcliffe”)
all our admissions arise from urgent referral from local GPs or via the Emergency Room
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Centre for Evidence-Based Medicine
The Protocol
At the time of discharge, death, or month’s end, each patient was reviewed and consensus reached on:
The primary diagnosis: the disease, syndrome or condition most
responsible for the patient’s admission to hospital
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Centre for Evidence-Based Medicine
The Protocol (cont.)
The Primary Intervention the treatment or other manoeuvre that
constituted our most important attempt to cure, alleviate, or care for the primary diagnosis
traced into the literature to determine its basis in evidence
– the Consultant’s “Instant Resource Book”– bibliographic data base searches
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Centre for Evidence-Based Medicine
Primary Interventions were Classified by Level:
Evidence from Randomised Control Trials (better yet: systematic reviews of all relevant, high-quality RCTs)
Convincing non-experimental evidence (unnecessary & unethical to randomise)
Interventions without substantial evidence
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Centre for Evidence-Based Medicine
Conclusions from E-B oriented General Medicine:
82% of our patients received evidence-based care.
treatments for 53% were justified by RCTs or systematic reviews of RCTs.
Of 28 relevant RCTs and SRs, 21 were accessible within seconds.
treatments for 29% were justified by convincing non-experimental evidence
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Centre for Evidence-Based Medicine
Evidence from RCTs (53%)
36% had Cardiovascular diagnoses:
» Ischaemic heart disease 17%» Heart failure 6%» Arrhythmia 2%» Thromboembolism 3%» Cerebrovascular 8%
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Centre for Evidence-Based Medicine
Evidence from RCTs (53%)
7% had taken poison 5% received chemotherapy or analgesia
for cancer 3 % had gastrointestinal disorders 2% had obstructive airways disease
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Centre for Evidence-Based Medicine
Convincing non-experimental evidence
(29%)
Infections 15% Cardiac disorders 7% Miscellany (non-compliance, drug
reactions, bowel or bladder neck obstruction, dehydration, micturition syncope) 7%
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Centre for Evidence-Based Medicine
Interventions without substantial evidence
(18%)
Specific symptomatic and supportive care for mild poisoning, non-cardiac chest pain, viral (non-herpetic) meningitis, terminal CNS disease, confusion, and food poisoning.
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Centre for Evidence-Based Medicine
Better Outcomes for Patients When EBM Is
Practised
E-B practise vs. Outcome in stroke (US): When cared for by E-B neurologists,
patients were 44% more likely to receive warfarin, and much more likely to be placed in a stroke care unit,
And were 22% less likely to die in the next 90 days. (Mitchell et al: stroke 1996;27:1937-43)
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Centre for Evidence-Based Medicine
Centres for Evidence-Based Surgery
E-B General/Vascular Unit in Liverpool:» 95% received evidence-based Rx
24% Level 1 71% Level 2
E-B Paediatric Unit in Liverpool:» 77% received evidence-based Rx
11% Level 1 66% Level 2
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Centre for Evidence-Based Medicine
Worse Outcomes for Patients When EBM Is Not
Practised:
In a city-wide study of E-B practise vs. Outcome in carotid stenosis:
Generated E-B indications for endarterectomy and reviewed 291 pts.
Found the surgical indications:» Appropriate in 33%»Questionable in 49%»Inappropriate in 18%
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Centre for Evidence-Based Medicine
Worse Outcomes for Patients When EBM Is Not
Practised
Stroke or death within the next 30 days: Expected (if left alone): 0.5% Expected (if properly selected and
operated): 1.5% Observed among operated patients (2/3
operated for questionable or inappropriate reasons): >5%
Wong et al. Stroke 1997;28: 891-8.
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Centre for Evidence-Based Medicine
Evidence-Based Ambulatory Paediatrics
54% of manoeuvres were evidence-based (“experts” had predicted <20%)» 77% of diagnostic manoeuvres» 67% of treatments» 59% of health promotion
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Centre for Evidence-Based Medicine
Centres for Evidence-Based
Psychiatry
In-Patients (Oxford)» 67% treated on the basis of RCTs
Out-Patient» >80% received evidence-based Rx
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Centre for Evidence-Based Medicine
Evidence-Based General Practice
122 consecutive consultations in a suburban (Leeds, UK) practice.
81% evidence-based:» 31% based on RCTs or overviews» 50% based on convincing non-experimental
evidence» 19% without substantial evidence
(Gill et al, BMJ 1996;312:819-21)
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Centre for Evidence-Based Medicine
Can we get evidence to the bedside?
Need it within seconds if it is to be incorporated into busy clinical rounds
Our initial attempts to bring the best evidence to a busy clinical team caring for 200+ admissions per month
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Centre for Evidence-Based Medicine
Searching for Evidence in the Month Before the Cart:
Expected searches = 98 Identified searching needs = 72 Only 19 searches (26%) carried out.
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Centre for Evidence-Based Medicine
Contents of the Cart:
Infra-red simultaneous stethoscope with 12 remote receivers.
Physical diagnosis text book and reprints (JAMA Rational Clinical Exam).
Notebook computer, computer projector, and pop-out screen.
Rapid printer.
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Centre for Evidence-Based Medicine
Contents of the Cart (cont):Library Round-Trip = 7 min
125 summaries (1-3 pp) of evidence previously appraised and summarised by Side A teams (in the form of “Redbook” entries or
Critically-Appraised Topics : “CATs”).
Access Time to the “bottom line” = 12 sec.Access Time to the “bottom line” = 12 sec.
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CAN FIND THE CAT IN 12 SECONDSMIS WITH HYPERGLYCAEMIA BENEFIT FROM INTENSIVE INSULIN THERAPY.
Clinical Bottom Line:Treating 9 hyperglycaemic MI patients iwth intensive insulin => 3 months will prevent oneadditional death over the next 3.4 years.
Appraised by: Sackett; 24 October 1997The Study: Non-blinded concealed randomised controlled trial with intention-to-treat.Swedish patients admitted with MI in the prior 24 hours with blood glucose >11 mmol/l with orwithout prior known diabetes. 50% thrombolysed; by discharge 80% given aspirin, 70% givenbeta-blockers, and 31% given ACE-inhibitors.Control group (N = 314; 314 analysed): Routine MI care (including aspirin and beta-blockers) but no (extra) insulin unless "clinically indicated" (43%, 45% and 49% on insulin at discharge, 3months, and 1 year)).Experimental group (N = 306; 306 analysed): Routine MI care plus glucose+insulin infusion for =>24 hours and qid insulin for =>3 months (87%, 80% and 72% on insulin at discharge, 3months, and 1 year).The Evidence:Outcome Time to
OutcomeCER EER RRR ARR NNT
death (allpatients)
3.4 years 0.439 0.333 24% 0.106 9
95%ConfidenceIntervals:
7% to 41% 0.030 to 0.182 5 to 34
Comments: 1. Benefit greatest in low risk patients (< 70 y/o, no prior MI, no CHF, no digitalis Rx) notpreviously on insulin (RRR 46%; ARR 0.15; NNT 7).2. PTCA and CABG done in 5% and 11% of controls and in 4% and 11% of intensive insulinpatients.3. Glucose 11.7 and 9.6 at 24 hours; 9 and 8.2 at discharge.4. 97% of deaths were cardiovascular, and most of the mortality benefit was seen afterdischarge. Expiry date: October 1998References: Malmberg K for the DIGAMI Study Group: Prospective randomised study of intensive insulintreatment on long term survival after acute myocardial infarction in patients with diabetesmellitus. BMJ 1997;314:1512-5.
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CAN OBTAIN THE BOTTOM LINE IN 2 SECONDS:
MIS WITH HYPERGLYCAEMIA BENEFIT FROM INTENSIVE INSULINTHERAPY.
Clinical Bottom Line: Treating 9 hyperglycaemic MI patients with intensiveinsulin => 3 months will prevent one additional deathover the next 3.4 years.
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CAN READ THE EVIDENCE IN 2 MINUTES
The Study: Non-blinded concealed randomised controlled trial with intention-to-treat.Swedish patients admitted with MI in the prior 24 hours with blood glucose >11 mmol/l with or without priorknown diabetes. 50% thrombolysed; by discharge 80% given aspirin, 70% given beta-blockers, and 31%given ACE-inhibitors.Control group (N = 314; 314 analysed): Routine MI care (including aspirin and beta-blockers) but no (extra) insulin unless "clinically indicated" (43%, 45% and 49% on insulin at discharge, 3 months, and 1 year)).Experimental group (N = 306; 306 analysed): Routine MI care plus glucose+insulin infusion for =>24 hours and qid insulin for =>3 months (87%, 80% and 72% on insulin at discharge, 3 months, and 1 year).
The Evidence:Outcome Time to
OutcomeCER EER RRR ARR NNT
death (allpatients)
3.4years
0.439 0.333 24% 0.106 9
95%ConfidenceIntervals:
7% to41%
0.030 to 0.182 5 to 34
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CAN STUDY THE ORIGINAL EVIDENCE FOR HOURS
Reference: Malmberg K for the DIGAMI Study Group: Prospective randomisedstudy of intensive insulin treatment on long term survival after acutemyocardial infarction in patients with diabetes mellitus. BMJ1997;314:1512-5.
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Centre for Evidence-Based Medicine
Contents of the Cart (cont):Library Round-Trip = 7 min
CD of Best EvidenceAccess Time to the “bottom line” = 26 sec.Access Time to the “bottom line” = 26 sec. CD of WinSPIRS (5-year clinical subsets)
Access Time to useful abstract = 90 secAccess Time to useful abstract = 90 sec. . (so used for filling Educational Rx after (so used for filling Educational Rx after rounds)rounds)
CD of the Cochrane Library (used for filling Educational Rx after rounds)(used for filling Educational Rx after rounds)
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Centre for Evidence-Based Medicine
Usefulness of the Cart:
81% of searches were for evidence that could affect diagnostic and/or treatment decisions.
90% of these searches were successful in finding useful evidence.
*
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Centre for Evidence-Based Medicine
Of the successful searches (from the perspective of the most junior responsible
team member):
52% confirmed diagnostic and/or management decisions
23% led to changes in existing decisions
25% led to additional decisions
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Centre for Evidence-Based Medicine
Searching for Evidence in a 3-day period after the Cart:
Expected searches = 10 Identified searching needs = 41 Only 5 searches (12%) carried out.
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Centre for Evidence-Based Medicine
Can we get evidence to the bedside?
Yes, and it will improve patient care. But can we provide it in a less
cumbersome form?
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Centre for Evidence-Based Medicine
EBM and Purchasing
In harmony:
When we clinicians stop doing things that are useless or harmful
When we use just-as-good but less expensive treatments, carers, and sites for care.
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Centre for Evidence-Based Medicine
What we could save in Oxford
by switching from:
LASIX frusemide: £ 90,000
simvastatin cerivastatin: £ 500,000
TENORMIN atenolol: £ 700,000
diclofenac ibuprofen: £ 1,000,000
Total: £ 2,290,000 how many hips would these savings
purchase?
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Centre for Evidence-Based Medicine
EBM and Purchasing
Still in harmony:
When we spend now to save later.
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Centre for Evidence-Based Medicine
EBM and Purchasing
In grudging collaboration:
Waiting lists, once we understand the opportunity costs of shortening them:» it’s not about money» it’s about what else we won’t be able to do
if we shorten them
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Centre for Evidence-Based Medicine
EBM and Purchasing
In conflict:
When we identify so strongly with a dying patient’s short-term goals that we use resources that we know would “add more QALYs” if used for other patients.
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Centre for Evidence-Based Medicine
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.
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Centre for Evidence-Based Medicine
EBM and E-B Guidelines
La mejor evidencia proviene de revisiones sistemáticas (como Cochrane) y/o revistas secundarias.» 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
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Centre for Evidence-Based Medicine
EBM and E-B Guidelines
But NO systematic review can (or should try to) identify the “4 B’s:» Burden» Barriers» Behaviours» Balance
Ello SOLO puede ser determinado a nivel local (o aún a nivel del paciente).
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Centre for Evidence-Based Medicine
1. Burden - Peso
La carga de enfermedad, discapacidad y mortalidad que pudiera ocurrir si la evidencia no fuera aplicada.
Las consecuencias de no hacer nada
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Centre for Evidence-Based Medicine
2. Barriers - Barreras
Valores y preferencias de los pacientes Geográficas Economicas Administrativas/Organización Usos y Costumbres Opinión de “Expertos”
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3. Behaviours - Comportamientos
Reacción al cambio de paradigmas. Costo personal del cambio. Igual para los pacientes
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4. Balance
El costo de oportunidad de aplicación de la guia en lugar de seguir actuando como antes.
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Centre for Evidence-Based Medicine
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.
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Centre for Evidence-Based Medicine
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.
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Centre for Evidence-Based Medicine
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.
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Centre for Evidence-Based Medicine
Applying a study result to my patient
Never interested in “generalising” Am interested in a special form of
extrapolation: particularising
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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?
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...
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Centre for Evidence-Based Medicine
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 ?
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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:
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.
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Centre for Evidence-Based Medicine
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
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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
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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
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)
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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
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%
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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.
Absolute Risk Increase = 3% at 1 yr, so ARI estimated to be 5% in 1.8 years
ACPJC 1994;120:52
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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
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%
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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%
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 ?
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Centre for Evidence-Based Medicine
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
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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):
for most of her patients, a bleed is only 1/5th as bad as a stroke
so the s~ is 0.2
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Centre for Evidence-Based Medicine
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)
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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.
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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!”