Grading Evidence in Medicine

Bill Cayley Jr MD MDivUW Health Augusta Family Medicine

Objectives

Participants will be able to:1. Describe the practice of evidence-based

medicine2. Discuss the presentation and classification of

evidence3. Discuss grading of evidence and integration into

clinical practice

What is“evidence-based

medicine?”

Two fundamental questions…

• What is the purpose of medicine?• How do I decide what to do?

You have to know where you’re going before deciding how to get there…

What is the purpose of medicine?

• Patient care• Public health• Research

Improving the quality of patients’ lives…

What is evidence-based medicine?

Evidence based medicine is the conscientious, explicit, and judicious use of current best

evidence in making decisions about the care of individual patients.

Sackett, et al. BMJ 1996;312:71-72

What is “EBM” NOT?

• What we have always done

• “Cookbook medicine”• Only a cost-cutting trick• Only randomized trials

Evidence based medicine IS… Tracking down the best

external evidence with which to answer our clinical questions…

EBM – a short history…

• JAMA 1992“EBM: a new approach…”

• JAMA 1993 – 2000“Users' Guides to the

Medical Literature”

• 1990s – 3 trends– Systematic reviews– Search engines– Knowledge distillation

and “push” services

Classification of evidence

How do I decide what to do?

The answer from EBM…“…use of current best

evidence…”

Evidence: systematic observation

Meta-AnalysisRandomized Controlled Trial

Uncontrolled TrialCase SeriesAnecdote

Evidence grading

• 1989 USPSTF– 5 levels of evidence

• Other systems:– CEBM– ACC– AAFP (SORT)– GRADE

• Detail, vs practicality

Grade Definition Suggestions for Practice

A The USPSTF recommends the service. There is high certainty that the net benefit is substantial.

Offer or provide this service.

B The USPSTF recommends the service. There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial.

Offer or provide this service.

C The USPSTF recommends against routinely providing the service. There may be considerations that support providing the service in an individual patient. There is at least moderate certainty that the net benefit is small.

Offer or provide this service only if other considerations support the offering or providing the service in an individual patient.

D The USPSTF recommends against the service. There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits.

Discourage the use of this service.

I Statement The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality, or conflicting, and the balance of benefits and harms cannot be determined.

USPSTF (as of May 2007)

GRADE (a work in progress)• GRADE classifies recommendations as strong or weak• Strong recommendations

– mean that most informed patients would choose the recommended management and that clinicians can structure their interactions with patients

accordingly

• Weak recommendations – mean that patients’ choices will vary according to their values and preferences,

and clinicians must ensure that patients’ care is in keeping with their values and preferences

Strength of recommendation

– determined by the balance between desirable and undesirable consequences of alternative management strategies, quality of evidence, variability in values and preferences, and resource use

Meta-AnalysisRandomized Controlled Trial

Uncontrolled TrialCase SeriesAnecdote

More systematic observation ► better evidence

Integrating evidence & practice

What type of outcome measures?

• Surrogate markers of disease:– Hb A1c, cholesterol, blood pressure

• Stage or extent of disease:– Diabetic ulcers, angiographic CAD, stroke

• Patient-oriented outcomes:– Mobility, suffering, longevity– Morbidity and mortality

Patient or disease oriented?• Disease-Oriented Outcomes.

– Intermediate, histopathologic, physiologic, or surrogate results

– Examples: blood sugar, blood pressure, flow rate, coronary plaque thickness

– May or may not reflect improvement in patient outcomes.• Patient-Oriented Outcomes.

– Outcomes that matter to patients and help them live longer or better lives

– Examples: including reduced morbidity, reduced mortality, symptom improvement, improved quality of life, or lower cost

Which outcomes????

• Topical antibiotics for bacterial conjunctivitis may improve early and late resolution rates, but nearly all cases ultimately have complete remission.

• Br J Gen Pract. 55: 962-4.

• Digoxin for symptomatic heart failure provides no significant difference in mortality but is associated with lower rates of hospitalization and of clinical deterioration.

• J Card Fail. 10:155-64.

• Long-acting beta-2 agonists for asthma are effective in reducing symptoms but may increase mortality or exacerbations.

• Cochrane Database of Systematic Reviews 2008, Issue 3. Art. No.: CD006363.

SORT

When guidelines conflict…

Questions of evidence• Were the clinical questions

different?• Were different studies

considered?• Were the results analyzed

differently?• Was the quality of evidence

assessed differently?

Questions of outcomes• Did the effect estimates for

important outcomes differ?• Did judgments about

evidence quality differ?• Were health consequences

weighed differently?• Were economic

consequences considered differently?

Systems applications

Informed decision-making

1) Physicians… • …must recognize the role of being the patient’s agent in

helping make informed decisions to maximize benefit at reasonable cost

2) Medical students and residents…• …should be educated to approach care as the patient’s

agent in making informed decisions, rather than solely as an autonomous decision maker

3) The evidence for and approach to developing standards should be standardized.

In short… EBM is the conscientious,

explicit, and judicious use of current best evidence in

making decisions about the care of individual patients.

EvidenceSystematic observation =

high-quality evidence

Patient-oriented evidencepreferable to

Stage of diseasepreferable to

Surrogate markers

For more information…

About EBM• Centre for Evidence-Based

Medicine (http://www.cebm.net/)

• Agency for Healthcare Research and Quality (http://www.ahrq.gov/clinic/epcix.htm)

Evidence sources• DynaMed

(www.dynamicmedical.com/)• Essential Evidence Plus

(www.infopoems.com/)• Cochrane Library

(www.cochrane.org/)• Database of Abstracts of Reviews

of Effectiveness (www.crd.york.ac.uk/crdweb/)

• FPIN (www.fpin.org/) • Clinical Evidence

(www.clinicalevidence.com/)