Using evidence in practice Nick Price 4 th

Using evidence in practice Nick Price 4 th April 2006

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

Schedule 1400 -1500. Overview of EBP Panorama programme on Herceptin 1515 -1530 -1615 Tea Group work Critically appraising an editorial. Working out some numbers Practice explaining risk to patients 1615 -1630 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 patient’s or population’s 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 Science Social Science Arts and humanities Ethics Adaptability, broad perspective Scientific Method Counting differences Understanding differences Humane Judgement Technical judgement Clinical Judgement

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

Panorama

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

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

Levels of evidence (I-1) a well done systematic review of 2 or more RCTs n (I-2) a RCT n (II-1) a cohort study n (II-2) a case-control study n (II-3) a dramatic uncontrolled experiment n (III) respected authorities, expert committees, etc. . (Good Old Boys Sitting Heroically At Tables? ) n (IV). . someone once told me. . . n

Gathering evidence Thorough Practical Medline search n SR and Meta-analyses n RCTs n Review articles n Observational Studies Clinical Evidence Cochrane Bandolier DTB Me. Re. C RCGP/RCPsych guidelines NICE guidelines NSF Local Guidelines Ask the consultant or others?

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

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

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

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 14 m per ticket per draw.

NNTs 2 ARI = 1/14 m per ticket per draw = 1/14 m x 2 per week with 1 ticket for each draw = 1/14 m x 2 x 5 for 5 years = 520/14 m NNT = 14 m/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. n Identifying appropriate literature needs to consider quality / rigour but also practicality. n Some stats are really quite easy but need to be used with care if you are to be honest. n I suggest that risks and benefits should be expressed in both absolute terms and relative terms and DON’T mix them up! n

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

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