An introduction to Evidence-based medicine

Steve Allen, MD

Scott & White Clinic

Temple, TX

Educational objectives

Define EBM Learn the steps to implement EBM Apply your new knowledge! Identify barriers to EBM implementation Determine strategies to overcome those

barriers

Evidence based medicine

EBM is the integration of current best research evidence with clinical expertise and patient values

EBM shifts authoritarianism to scientific skepticism

EBM is an active process Life-long Problem based learning

History of EBM

Valid data: Randomized clinical trials rare into 1960s and beyond

“EBM” coined in 1992 – Guyatt et al @ McMaster Univ

0

500

1000

1500

2000

2500

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1992 2003

Overall

Ob/Gyn

“EBM” articles, PubMed

n = 6

The EBM paradigm shift

Understanding of pathophysiologic principles

Clinical experience Common sense Reliance on expert

opinion

Knowledge of pathophysiology is necessary but insufficient

Systematic approach increases certainty of diagnostic validity & management strategies

Formal rules of evidence

Strength of RecommendationsUSPSTF 2004

A. Strongly recommends that clinicians provide [the service] to eligible patients: good evidence that [the service] improves important health outcomes; benefits substantially outweigh harms.

B. Recommends that clinicians provide [this service] to eligible patients: at least fair evidence.

Strength of RecommendationsUSPSTF 2004

C. No recommendation for or against routine provision of [the service]; the balance of benefits and harms is too close to justify a general recommendation.

D. Recommends against routinely providing [the service] to asymptomatic patients.

E. Evidence is insufficient to recommend for or against routinely providing [the service].

Quality of EvidenceUSPSTF 2004

Good: Consistent results from well-designed, well-conducted studies in representative populations that directly assess effects on health outcomes.

Fair: Evidence sufficient to determine effects on health outcomes, but the strength of the evidence is limited by the number, quality, or consistency of the individual studies, generalizability to routine practice, or indirect nature of the evidence on health outcomes.

Poor: Evidence insufficient to assess the effects on health outcomes.

The need for EBM

Daily need for valid information 5x/inpatients 2x/3 outpatients

Inadequacy of traditional sources – out of date or wrong

Disparity between skills and knowledge over time Time restrictions

seconds per patient max 30 min/wk

Developments which facilitate the practice of EBM

Strategies for appraising evidence (ex: meta-analysis)

Systematic reviews & concise summaries (ex: Cochrane Collaboration; practice guidelines)

Information systems to deliver data efficiently

Implementation of EBM

“EBM levels the intellectual playing field” * Everyone’s opinion counts equally –

regardless of rank Opinions valued only to the extent that they

are supported by scientific evidence When a question arises, it should be

addressed through formal review – rather than by faculty edict

* Grimes DA. OG 1995;86:451

EBM: the process

1. Convert information need into focused question2. Find the best evidence to answer the question3. Critically appraise the evidence for its validity and

clinical usefulness4. Integrate the critical appraisal with clinical expertise

and the patient’s unique circumstances5. Evaluate performance – seek ways to improve next

time

Usefulness of EBM

Usefulness of a source

Relevance x Validity

Work=

POEM trumps DOE

“ The influence of obesity and diabetes on the prevalence of macrosomia”

Ehrenberg et al

AJOG 2004;191;964

“The influence of obesity and diabetes on the risk of cesarean delivery”

Ehrenberg et al

AJOG 1004;191:969

EBM: individualization

Not all questions require the maximum work “just in time” sources for common questions

Low work; rely on someone else to do the critical analysis

ex: practice guidelines “just in case” sources for complex and

atypical casesHigh work; you must do the critical analysis

yourself

EBM: the process

1. Convert information need into focused question2. Find the best evidence to answer the question3. Critically appraise the evidence for its validity and

clinical usefulness4. Integrate the critical appraisal with clinical

expertise and the patient’s unique circumstances5. Evaluate performance – seek ways to improve

next time

Clinical case #1

A 29 yo obese white P1001 with HHT (hereditary hemorrhagic telangiectasia syndrome) and Type 2 diabetes presents for prenatal care at 14 weeks gestational age.

List 3 pertinent questions to help you provide optimal medical care to this patient.

1)

2)

3)

Well-formulated clinical questions

Background questions Ask for general

knowledge about a disorder

2 essential components Question root (who, what,

where … ) & a verb The disorder

Foreground questions Ask for specific knowledge

about pt management 3-4 essential components

Patient and/or problem Intervention Comparison intervention Clinical outcomes

Types of questions

0102030405060708090

100

Novice R2 Expert

Background

Foreground

Topics for well-formulated clinical questions

Clinical findings Etiology Clinical

manifestations Differential diagnosis

Diagnostic tests

Prognosis Therapy Prevention Experience &

meaning Self-improvement

Clinical case #2

A 29 yo obese white P1001 with Type 2 diabetes presents for prenatal care at 14 weeks gestational age. For the last 2 years she has taken glyburide to control her DM.

List 3 pertinent questions to help you provide optimal medical care to this patient.

1)

2)

3)

Types of questions

0102030405060708090

100

Novice R2 Expert

Background

Foreground

Clinical case #2

Regarding your most important question Question:

Your best answer (without searching):

Initial evidence resource:

EBM: the process

1. Convert information need into focused question2. Find the best evidence to answer the question3. Critically appraise the evidence for its validity and

clinical usefulness4. Integrate the critical appraisal with clinical

expertise and the patient’s unique circumstances5. Evaluate performance – seek ways to improve

next time

EBM on EBM

Does providing evidence based care improve outcomes for patients?

The data are not yet available! … (But that is not an excuse to ignore EBM)

Clinical case #2

A 29 yo obese white P1001 with Type 2 diabetes (Rx: glyburide) presents for prenatal care at 14 weeks gestational age.

Pertinent questions:

1) Glyburide’s mechanism of action?

2) Glyburide’s safety for pregnancy?

3) Glyburide’s efficacy during pregnancy?

Clinical case #2 most important questions

Question: Glyburide’s mechanism of action?

Your best answer (without searching): Promotes insulin secretion

Initial evidence resource: Micromedex

Clinical case #2most important questions

Question: Glyburide’s mechanism of action?

Your best answer (without searching): Promotes insulin secretion

Initial evidence resource: Micromedex

Your final answer:

Clinical case #2 most important questions

Question: Glyburide’s safety for pregnancy?

Your best answer (without searching): No great risk for teratogenesis

Initial evidence resource: PubMed search

Clinical case #2most important questions

Question: Glyburide’s safety for pregnancy?

Your best answer (without searching): No great risk for teratogenesis

Initial evidence resource: PubMed search

Your final answer:

Clinical case #2most important questions

Question: Glyburide’s efficacy during pregnancy?

Your best answer (without searching): Fairly effective BS control

Initial evidence resource: PubMed Search

Clinical case #2most important questions

Question: Glyburide’s efficacy during pregnancy?

Your best answer (without searching): Fairly effective BS control

Initial evidence resource: PubMed Search

Your final answer:

Barriers to EBM

Time Critical evaluation skills Institutional/academic chauvinism Reluctance to question authority Medical inertia Numerators of one Technological disability Lack of high quality evidence for many

clinical questions

The End