1. Associate Fellow, Centre for Evidence-based Medicine, Oxford
Therapies
Dr Bob Phillips
Associate Fellow, Centre for Evidence-based Medicine, Oxford

2. Therapy Ask a question Acquire some articles Appraise the evidence
Apply the findings
Assess your performance
Repeat – SPIRAL learning
Five steps
Main learning area highlighted
Then …
Describe clinical scenario
Story of a baby irrascible, unsettled, crying awkwardly and ?drawing up legs/pulling at ears
Typanic temperature 37.4 but looked slightly iffy. Repeated cases of tympanics being ??, esp. as new US colleague obsessed wqith sticking thermometers up bottoms.

3. Therapies To treat or not to treat? Validity Importance Applicability
Explain there is a condition known as Higgenbottom’s Syndrome
Makes people drink excessive amounts of alcohol and fight in pubs
Trials recently with a therapy, Balay, which had been shown to look promising in animal experiments
A new paper published -J Dance Therapeutics - and you want to know if you invest in setting up the treatment programme
Validity - is the paper likely to be true
Importance - size of effect
Applicability - can it work for me/my setting

4. Therapies Validity Was it randomised? Was the allocation concealed?
Were the all the subjects analysed correctly?
Was it blinded?
Were the groups similar?
Validity
randomisation - bias concealment - bias
analysis - how many - 80% rule of thumb
why? Drop out make it insecure -- too bad to work through / side effects?
Psych -- new antipsychotic -- appears to work but V low follow up -- why? -- side effects intolerable, people stopped taking it and stopped attending medical clinics
ITT analysis - avoid the problems of having really bad ones transferred out of experimental group (or into experimental group)
Stroke / carotid trials -- swapped out of the surgery arm cause too crock
Neonates -- swapped into oscillatory ventilation as rescue strategy
blinding - diff twix blind and concealed
started equally - lots of very old people in a stroke trial? More boys in asthma?
treated equally - asthma trial - ventolin vs ventolin/atrovent -- if ventolin arm more got steroid then reduced effectiveness of ipratropium

5. Therapies Importance What were the results? Over what time period?
With what precision?
What were the results?
What was the outcome -- important?
How long did it take - esp important in comparisions
(talk about how later …)
What precision - ‘p’ vs CI Clinical and statistical significance

6. Therapies Number needed to treat Relative risk reduction
Absolute risk reduction
Event rates
Basic EBM number building block
NOT statistics - just adding up, taking away and dividing
back to Balay
draw table
Fighting Reading Camus
Balay 10 40
Normal 35 15

7. Therapies Event rates Control event rate (CER)
n with event / total
Control event rate (CER)
Experimental event rate (EER)
Work though
EER (balay) = 0.2
CER (normal) = 0.7

8. Therapies Absolute risk reduction Relative risk reduction
difference in two event rates
CER - EER = ARR
Relative risk reduction
proportion of control rate
CER-EER / CER = RRR
ARR = = 0.5
RRR = 0.5 / 0.7 ~ 70%

9. Therapies Number needed to treat
number of extra patients you need to treat to prevent one bad outcome
1 / ARR = NNT
Work it out 1 / 0.5 = 2
explain its for every two people in Balay, then one will not fight who would have done if left in the normal programme
not that you have a 50% success rate
interesting aside
RRR same if instead of as above it was
Fighting Reading Camus
Balay 1 49
Normal
EER = 0.02
CER = RRR~70% ARR=0.05 NNT=20

10. Therapies 95% confidence interval
range within which the true value falls with 95% confidence
use computer (e.g. CATMaker)
Point estimate of the truth
Assume the truth is out there
Bell shaped curve around the truth
95% why? Coins trick

11. Therapies Application Can it be applied to my patient?
Can it be done here?
How do patient values affect the decision?
Look at the differences between patients in trial and on street - too different? How different? - ‘f’
Is it feasible
Do values matter - and how much? - look at the LBHH

12. Therapies Is it valid? Is it important? Does it apply? NNT for what
over how long
with what precision
Does it apply?
summarise

13. Junior Fellow, Centre for Evidence-based Medicine, Oxford
Therapies
Dr Bob Phillips
Junior Fellow, Centre for Evidence-based Medicine, Oxford