Using evidence in practice Nick Price 4 th April 2006

Objectives To have an overall understanding of the concept of evidence based practice. To have an overall understanding of the concept of evidence based practice. To critique how evidence is presented in journals and by journalists. To critique how evidence is presented in journals and by journalists. Raise awareness of other factors that influence clinical decision making. Raise awareness of other factors that influence clinical decision making. To be able to apply simple statistics in practice. To be able to apply simple statistics in practice. To be able to present these to patients, minimising bias. To be able to present these to patients, minimising bias. To develop some of the skills in this area required to pass the MRCGP. To develop some of the skills in this area required to pass the MRCGP.

Schedule Overview of EBP Panorama programme on Herceptin Tea Group work Critically appraising an editorial. Working out some numbers Practice explaining risk to patients Summary and evaluation (plenary)

What is evidence based practice?

Evidence based medicine? Maybe it is the application of the best available scientific knowledge to the patients or populations clinical problem? Or Evidence-based medicine is the integration of best research evidence with clinical expertise and patient values Sackett et al (2000)

A model of influences in clinical decision making ScienceSocial Science Scientific Method Counting differences Understanding differences Technical judgement Arts and humanities Ethics Adaptability, broad perspective Humane Judgement Clinical Judgement

Principles of a health care system equity equity effectiveness effectiveness efficiency efficiency appropriateness appropriateness accessibility accessibility responsibility responsibility humanity humanity quantitative qualitative RCT Cohort studies Case control studies Descriptive studies Systematic review Meta-analysis

Panorama

Should I sell my house to pay for Herceptin, Doctor? How would you gather evidence?

First define your question PICO Population Population Intervention(s) Intervention(s) Comparison Comparison Outcome. Outcome.

Levels of evidence (I-1) a well done systematic review of 2 or more RCTs (I-1) a well done systematic review of 2 or more 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, etc.. (III) respected authorities, expert committees, etc.. (Good Old Boys Sitting Heroically At Tables?) (IV)....someone once told me... (IV)....someone once told me...

Gathering evidence ThoroughPractical Medline search SR and Meta-analyses RCTs Review articles Observational Studies Clinical Evidence Cochrane Bandolier DTB MeReC RCGP/RCPsych guidelines NICE guidelines NSF Local Guidelines Ask the consultant or others?

What I actually did for Herceptin Medline – got nowhere really Medline – got nowhere really – got nowhere really – got nowhere really Asked my mates a bit. Asked my mates a bit. – editorial and then references from that. – editorial and then references from that. Could have done what?

Making sense of numbers Relative risk Relative risk Absolute risk Absolute risk Absolute risk reduction / harm Absolute risk reduction / harm NNT NNT NNH NNH Hazard Ratio Hazard Ratio Cost per case / QALY Cost per case / QALY

So lies damn lies and statistics? Absolute risk / benefits often sound small Absolute risk / benefits often sound small Relative risk / benefits can sound big Relative risk / benefits can sound bige.g. Your chance of winning the lottery with 2 tickets as opposed to one is increased by 1 in 14million Your chance of winning the lottery with 2 tickets as opposed to one is increased by 1 in 14million Your chance of winning the lottery with 2 tickets as opposed to one is increased by 100% Your chance of winning the lottery with 2 tickets as opposed to one is increased by 100%

Numbers Needed to Treat The average number of people from a defined population you would need to treat with a specific intervention for a given period of time to achieve one beneficial outcome. NNT = 1 / ARR Can you calculate this for winning the lottery jackpot? Assume chance of winning is 1 in 14m per ticket per draw.

NNTs 2 ARI = 1/14m per ticket per draw = 1/14m x 2 per week with 1 ticket for each draw draw = 1/14m x2 x52 x5 for 5 years = 520/14m NNT = 14m/520 = 27,000 approx i.e. 27,000 people have to buy 2 tickets a week for 5 years for one person to win the jackpot

Summary Trials are there to inform clinical decision making. Trials are there to inform clinical decision making. Identifying appropriate literature needs to consider quality / rigour but also practicality. Identifying appropriate literature needs to consider quality / rigour but also practicality. Some stats are really quite easy but need to be used with care if you are to be honest. Some stats are really quite easy but need to be used with care if you are to be honest. I suggest that risks and benefits should be expressed in both absolute terms and relative terms and DONT mix them up! I suggest that risks and benefits should be expressed in both absolute terms and relative terms and DONT mix them up!

Some reading / resources: Greenhalgh T (2000) How to Read a Paper: The basics of evidence based medicine. London BMJ Publishing Greenhalgh T (2000) How to Read a Paper: The basics of evidence based medicine. London BMJ Publishing McGovern D P B, Summerskill W S M, McManus R (2001) Evidence-based medicine in General Practice. Oxford BIOS Scientific. OR McGovern D P B, Summerskill W S M, McManus R (2001) Evidence-based medicine in General Practice. Oxford BIOS Scientific. OR Sackett DL, Strauss S, Richardson WS, Rosenberg W, Hayes RB (2000) Evidence- based Medicine: How to practice and Teach EBM. Edinburgh Churchill Livinstone Sackett DL, Strauss S, Richardson WS, Rosenberg W, Hayes RB (2000) Evidence- based Medicine: How to practice and Teach EBM. Edinburgh Churchill Livinstone

Tea time Then: Reviewing the editorial and doing some sums. Back here for 1615 for close and evaluation