Using evidence in practice Nick Price 4 th April 2006.

Using evidence in Using evidence in practicepractice

Nick Price 4Nick Price 4thth April 2006 April 2006

ObjectivesObjectives To have an overall understanding of the To have an overall understanding of the

concept of evidence based practice.concept of evidence based practice. To critique how ‘evidence’ is presented in To critique how ‘evidence’ is presented in

journals and by journalists.journals and by journalists. Raise awareness of other factors that influence Raise awareness of other factors that influence

clinical decision making.clinical decision making. To be able to apply simple statistics in To be able to apply simple statistics in

practice.practice. To be able to present these to patients, To be able to present these to patients,

minimising bias.minimising bias. To develop some of the skills in this area To develop some of the skills in this area

required to pass the MRCGP.required to pass the MRCGP.

ScheduleSchedule

1400-15001400-1500 Overview of EBPOverview of EBPPanorama programme on Panorama programme on

HerceptinHerceptin..

1515-1530 1515-1530 TeaTea1530-16151530-1615 Group work Group work

Critically appraising an Critically appraising an editorial.editorial.

Working out some numbersWorking out some numbersPractice explaining risk to Practice explaining risk to

patientspatients1615-16301615-1630 Summary and evaluation Summary and evaluation

(plenary)(plenary)

What is evidence based What is evidence based practice?practice?

Evidence based Evidence based medicine?medicine?

Maybe it is the application of the best Maybe it is the application of the best available scientific knowledge to the available scientific knowledge to the patient’s or population’s clinical patient’s or population’s clinical problem?problem?

OrOr

‘‘Evidence-based medicine is the Evidence-based medicine is the integration of best research integration of best research evidence with clinical expertise and evidence with clinical expertise and patient values’ Sackett et al (2000)patient values’ Sackett et al (2000)

A model of influences inA model of influences inclinical decision makingclinical decision making

ScienceScience Social ScienceSocial ScienceScientific MethodScientific MethodCounting differences Counting differences

Understanding differencesUnderstanding differences

Technical judgementTechnical judgement

Arts and Arts and humanitieshumanities

EthicsEthics

Adaptability, broad Adaptability, broad perspectiveperspective

Humane JudgementHumane Judgement

Clinical JudgementClinical Judgement

Principles of a health Principles of a health care systemcare system

equityequity effectivenesseffectiveness efficiencyefficiency appropriatenessappropriateness accessibilityaccessibility responsibilityresponsibility humanityhumanity

quantitative

qualitative

RCTCohort studiesCase control studiesDescriptive studies

Systematic reviewMeta-analysis

PanoramaPanorama

‘‘Should I sell my house Should I sell my house to pay for Herceptin, to pay for Herceptin,

Doctor?’Doctor?’

How would you gather How would you gather evidence?evidence?

First define your questionFirst define your questionPICOPICO

PPopulationopulation IIntervention(s)ntervention(s) CComparisonomparison OOutcome.utcome.

Levels of evidenceLevels of evidence

(I-1) a well done systematic review of 2 or (I-1) a well done systematic review of 2 or more RCTsmore RCTs

(I-2) a RCT(I-2) a RCT (II-1) a cohort study(II-1) a cohort study (II-2) a case-control study(II-2) a case-control study (II-3) a dramatic uncontrolled experiment(II-3) a dramatic uncontrolled experiment (III) respected authorities, expert committees, (III) respected authorities, expert committees,

etc..etc..

((GGood ood OOld ld BBoys oys SSitting itting HHeroically eroically AAt t TTables?)ables?) (IV)....someone once told me...(IV)....someone once told me...

Gathering evidenceGathering evidenceThoroughThorough

PracticalPractical

Medline searchMedline search SR and Meta-analysesSR and Meta-analyses RCTsRCTs Review articlesReview articles Observational StudiesObservational StudiesClinical EvidenceClinical EvidenceCochraneCochraneBandolierBandolierDTB MeReCDTB MeReCRCGP/RCPsych guidelinesRCGP/RCPsych guidelinesNICE guidelinesNICE guidelinesNSFNSFLocal GuidelinesLocal GuidelinesAsk the consultant or Ask the consultant or

others?others?

What I actually did for What I actually did for HerceptinHerceptin

Medline – got nowhere reallyMedline – got nowhere really www.scholar.google.comwww.scholar.google.com – got – got

nowhere reallynowhere really Asked my mates a bit.Asked my mates a bit. www.bmj.comwww.bmj.com – editorial and then – editorial and then

references from that.references from that.

Could have done what?Could have done what?

Making sense of Making sense of numbersnumbers

Relative riskRelative risk Absolute riskAbsolute risk Absolute risk reduction / harmAbsolute risk reduction / harm NNTNNT NNHNNH Hazard RatioHazard Ratio Cost per case / QALYCost per case / QALY

So lies damn lies and So lies damn lies and statistics?statistics?

Absolute risk / benefits often sound smallAbsolute risk / benefits often sound small Relative risk / benefits can sound bigRelative risk / benefits can sound big

e.g. e.g. Your chance of winning the lottery with 2 Your chance of winning the lottery with 2

tickets as opposed to one is increased by tickets as opposed to one is increased by 1 in 14million1 in 14million

Your chance of winning the lottery with 2 Your chance of winning the lottery with 2 tickets as opposed to one is increased by tickets as opposed to one is increased by 100%100%

Numbers Needed to Numbers Needed to TreatTreat

The average number of people from a The average number of people from a defined population you would need to defined population you would need to treat with a specific intervention for a treat with a specific intervention for a given period of time to achieve one given period of time to achieve one beneficial outcome.beneficial outcome.

NNT = 1 / ARRNNT = 1 / ARRCan you calculate this for winning the Can you calculate this for winning the

lottery jackpot?lottery jackpot?Assume chance of winning is 1 in 14m Assume chance of winning is 1 in 14m

per ticket per draw.per ticket per draw.

NNTs 2NNTs 2

ARI = 1/14m per ticket per drawARI = 1/14m per ticket per draw= 1/14m x 2 per week with 1 ticket = 1/14m x 2 per week with 1 ticket

for eachfor each drawdraw= 1/14m x2 x52 x5 for 5 years= 1/14m x2 x52 x5 for 5 years= 520/14m= 520/14m

NNT = 14m/520 = 27,000 approxNNT = 14m/520 = 27,000 approxi.e. 27,000 people have to buy 2 tickets a i.e. 27,000 people have to buy 2 tickets a

week for 5 years for one person to win week for 5 years for one person to win the jackpotthe jackpot

SummarySummary Trials are there to inform clinical Trials are there to inform clinical

decision making.decision making. Identifying appropriate literature needs Identifying appropriate literature needs

to consider quality / rigour but also to consider quality / rigour but also practicality.practicality.

Some stats are really quite easy but Some stats are really quite easy but need to be used with care if you are to need to be used with care if you are to be honest.be honest.

I suggest that risks and benefits should I suggest that risks and benefits should be expressed in both absolute terms and be expressed in both absolute terms and relative terms and DON’T mix them up!relative terms and DON’T mix them up!

Some reading / Some reading / resources:resources:

Greenhalgh T (2000) Greenhalgh T (2000) How to Read a How to Read a Paper: The basics of evidence based Paper: The basics of evidence based medicine.medicine. London BMJ Publishing London BMJ Publishing

McGovern D P B, Summerskill W S M, McGovern D P B, Summerskill W S M, McManus R (2001) McManus R (2001) Evidence-based Evidence-based medicine in General Practice.medicine in General Practice. Oxford Oxford BIOS Scientific. ORBIOS Scientific. OR

Sackett DL, Strauss S, Richardson WS, Sackett DL, Strauss S, Richardson WS, Rosenberg W, Hayes RB (2000) Rosenberg W, Hayes RB (2000) Evidence-Evidence-based Medicine: How to practice and based Medicine: How to practice and Teach EBMTeach EBM. Edinburgh Churchill . Edinburgh Churchill LivinstoneLivinstone

Tea timeTea time

Then:Then:

Reviewing the editorial and doing Reviewing the editorial and doing some sums.some sums.

Back here for 1615 for close and Back here for 1615 for close and evaluationevaluation