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MPP3

Lecture 6

Dr A Kostzrewski

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What is evidence?

The hierarchy of evidence

What is evidence-based medicine?

Role of NICE, SIGN, PRODIGY, NSF,

Cochrane Library

Implications of national guidance for

practice

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What is evidence?

A patient tells you that the atenolol really helps toreduce her angina attacks.

A group of specialists from the local area havedecided by consensus that beta-blockers should beused as first-line treatment for angina.

A RCT of 10,000 people shows lower incidence ofMIs and of premature death in those treated withbeta-blockers compared with amlodipine.

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The Hierarchy of evidence for

effectivenessI Systematic reviews of RCTs, or RCTs

II Cohort studies

III Case-control studies

IV Cross-sectional studies, case reports,

case series

V Consensus/expert opinion

www.nice.org.uk www.cebm.net

http://www.nice.org.uk/http://www.cebm.net/http://www.cebm.net/http://www.nice.org.uk/

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The Hierarchy of evidence for

effectiveness Systematic reviews of RCTs, or RCTs

Cohort studies

Case-control studies

Cross-sectional studies, case reports,

case series

Consensus/expert opinion

Increasing bias

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Systematic reviews

Synthesis of studies

Available studies are systematically gathered

and reviewed according to pre-defined methods i.e. methods are explicit and reproducible

Meta-analysis (pooling of data) undertaken if

same outcomes used across studies

Example Cochrane library of systematic

reviews (http://www.cochrane.org/index.htm)

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Systematic Review

Study 1 Study 2 Study 3 Study 4

Combined results

Meta-analysis

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Randomised Controlled Trial

Allocate intervention and comparator(s)randomly to selected population

Follow-up and compare groups in terms ofpre-defined outcomes

Best design for evaluating interventions

Disadvantages - expensive, time-

consuming, ?generalisability

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RCT

Control group

(different treatment

or none)

Treatment group Follow-up

Follow-up

Compare

groups

Selected

population

Random

assignment

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Cohort

Comparison of groups, selected on basis ofpresence or absence of risk factor (e.g.exposure or intervention)

Follow-up from exposure (event orintervention) to outcome (predefined)

Best design for prognostic studies

Potential selection bias, loss to follow-up HRT example different results for RCT vs

cohort studies

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Cohort

Comparison group

e.g. women who are

not incontinent

Group of interest e.g. women

who are incontinent

Follow over time

Follow over time

Compare

outcomes (pre-

defined)

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Case-control

Compare a group that has an outcome with matchedcontrols

Controls differ only in exposure to possible causal agent

Retrospective i.e. starts with outcome, and looks back to identify

whether there is an association between exposure andoutcome by identifying non-cases

Useful when examining risk factors for disease (rareconditions)

Potential recall bias

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Case-control

Take histories

Take histories

Compare

histories

Group of interest (with

outcome)

Comparison group

(no outcome,

matched with

group of interest)

Draw

conclusion

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Cross-sectional

Survey

Examine exposure and outcome in a

population at single time period

Useful in epidemiology and public health

e.g. prevalence

Can identify associations but not explain them

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Cross-sectional

Population surveyed

at one point in time

Population

Population with

exposure and

outcome

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Case-series

Based on medical histories

No comparison group

New treatments or tests described in a studywith no control group also fall into this category

Descriptive only can suggest trends but do not

provide explanations or show associations

between cause and effect

Open to selection bias

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Case-series

Patients Records

Report

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The Hierarchy of evidence for

effectiveness Systematic reviews of RCTs, or RCTs

Cohort studies

Case-control studies

Cross-sectional studies, case reports,

case series

Consensus/expert opinion

Increasing bias

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Answer our question of what is

evidence.A patient tells you that the atenolol really helps to

reduce her angina attacks.

A group of specialists from the local area has decided

by consensus that beta-blockers should be used as

first-line treatment for angina.

A RCT of 10,000 people shows lower incidence of

MIs and of premature death in those treated with

beta-blockers compared with amlodipine.

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What is evidence-based medicine?

Various definitions

Involves judicious use of evidence in

managing patients

Hierarchy of evidence is used to grade

recommendations in guidelines (strength

of evidence)

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National Institute for Health and Clinical

Excellence (NICE)

Four programmes of work

Clinical guidelines

Technology appraisals

Single technologies e.g. drugs or groups of similar drugs e.g.

Herceptin, proton pump inhibitors

Interventional procedures

Public health guidance e.g. workplace smoking

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NICE and evidence based

practice NICE guidance is based on best available

evidence

e.g. for a question about effectiveness, if there issystematic review that considers the question noneed to go further

also includes consideration of cost-effectiveness

Best available clinical/cost evidence +clinical interpretation/ input = NICEguidance

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Scottish Intercollegiate

Guidelines Network (SIGN)

NICE guidance applies to both England

and Wales

SIGN covers Scotland

Similar methodology

www.sign.ac.uk

http://www.sign.ac.uk/http://www.sign.ac.uk/

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PRODIGY(CKS NHS Clinical Knowledge Summaries NHS Evidence)

A source of clinical knowledge for the

NHS about the common conditions

managed in primary and first contact care

Assimilates guidance from other sources

e.g. NICE, other best available evidence

http://www.prodigy.clarity.co.uk

http://www.prodigy.clarity.co.uk/http://www.prodigy.clarity.co.uk/

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National Service Frameworks

Department of Health

Set standards for service delivery

Examples coronary heart disease, older

people, long-term conditions

Relationship between NICE and NSFs

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Implications of national guidance

for practice

Follow as best practice

NICE Technology Appraisals

The NHS must demonstrate funding is

available

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..implications for pharmacy practice

Know what the current national guidance

is (and why)

..beware, things change new evidence

Ask yourselves how old the guidance is

Where also would you go?

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Conclusions What is evidence?

The hierarchy of evidence

What is evidence-based medicine?

Role of NICE, SIGN, PRODIGY, NSF,Cochrane Library

Implications of national guidance for

practice

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