Evidence Based Medicine: An overview for Higher Specialist Training in Paediatrics

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Evidence Based MedicineAn overview for Higher
Specialist Training in Paediatrics

• The James Cook University Hospital
• November 21st 2007
• Mr Tony Roberts
• Clinical Effectiveness Specialist Advisor
• South Tees Hospitals NHS Trust, Tees PCTs and
  Durham University

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The brief

• Overview of evidence based medicine including
• Study designs
• Statistics and methodology
• Bias
• Confounding variables
• As youre being Cochraned this afternoon Ill
  try and cover everything else
• Of yes, and a bit on Cauldicott, data protection
  and Research Management and Governance (RMG)

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Caldicott and Data Protection

• The Caldicott Report (December 1997) and
  Executive Letter (January 1999) set in motion a
  process of continuous improvement in medical
  confidentiality within the National Health
  Service.
• Caldicott Guardians have been appointed in all
  Trusts (for South Tees it is Prof Mike Bramble,
  the Medical Director), whose functions are to
  ensure that data handling is in accordance with
  the recommendations of the Caldicott Committee
  and requirements of the Data Protection Act.
• These especially affect data with Personal
  Identifiable Information (PII).

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Caldicott principles

• The principles in the Caldicott Report are
  summarised below1. Justify the purpose(s) for
  using patient data 2. Don't use
  patient-identifiable information unless it is
  absolutely necessary 3. Use the minimum
  necessary patient-identifiable information 4.
  Access to patient-identifiable information should
  be on a strict need to know basis 5. Everyone
  should be aware of their responsibilities to
  maintain confidentiality 6. Understand and
  comply with the law, in particular the Data
  Protection Act

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Data Protection Act Principles

• The information to be contained in personal data
  shall be obtained, and personal data shall be
  processed, fairly and lawfully.
• Personal data shall be held only for one or more
  specified and lawful purposes.
• Personal data held for any purpose or purposes
  shall not be used or disclosed in any manner
  incompatible with that purpose or those purposes.
  
• Personal data held for any purpose or purposes
  shall be adequate, relevant and not excessive in
  relation to that purpose or those purposes.
• Personal data shall be accurate and, where
  necessary, kept up to date.
• Personal data held for any purpose or purposes
  shall not be kept for longer than is necessary
  for that purpose or those purposes.
• An individual shall be entitled -
• at reasonable intervals and without undue delay
  or expense -
• to be informed by any Data User whether he holds
  personal data of which that individual is the
  subject
• to have access to any such data held by a Data
  User and
• where appropriate, to have such data corrected or
  erased.
• Appropriate security measures shall be taken
  against unauthorised access to, or alteration,
  disclosure or destruction of, personal data and
  against loss or destruction of personal data.

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Library resourcesthis is ours but use your
local one or the National one www.library.nhs.uk )
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JAMA User Guides
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Evidence-Based PracticeImplementing research
findings in practice
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Types of study

• Secondary Research
• Systematic reviews and meta-analysis
• Primary Research
• Experimental
• Randomised trials (RCTs)
• Analytic (epidemiological)
• Cohort studies
• Case-control studies
• Descriptive
• Surveys, incidence/prevalence studies etc
• Also includes the vitally important diagnostic
  studies which have one group but two tests per
  patient
• Audit and Evaluation
• Audits have standards, evaluations tend not to

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Sample size

• 4 elements
• The number of patients (sample size)
• The effect size
• ?
• 1-?

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Types of error
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Validity

• Internal validity
• External validity
• Systematic bias
• Random bias
• Reliability

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Lots of places to look up which statistical test
to use (and impossible to summarise in the
available time today)
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P values
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An example RCTs
I Wait-And-See Prescription for antibiotics
Spiro DM et al. Wait-and-See Prescription for the
Treatment of Acute Otitis Media. A Randomized
Controlled Trial. JAMA 2006 2961235-41 PICO
Intervention
O Filling of the antibiotic prescription and
clinical course
Population/ patients/ problem
Comparison/control
P Children with AOM aged 6 months to 12 years
seen in ER
C Standard Prescription for antibiotics
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The main EBM measures for RCTs

• WASP SP
• n 132 133
• Prescription not filled 82 17
• 62 13
• Absolute Risk Reduction 62 - 13 49 (40 to
  60)
• NNT 100/49 2 (1.7 to 2.5)
• Relative Risk 13/62 0.43 (0.35 to 0.55)
• Relative Risk Reduction 1-RR 67 (45 to
  65)

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The NNT in words

• For every 2 patients who receive a WASP for
  antibiotics, compared to a SP for antibiotics,
  there will be one less prescription filled.
• (In this study there was no detectable
  difference in the clinical course of the AOM
  between groups).

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Adjusting estimates

• NNT 1/(PEER x RRR)

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95 CIs odds vs risks
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Some places on the web to go to look at EBM more
slowly!

• http//www.evidencebasedpractice.org.uk
• http//stis-001/default.asp?sitelibrary
• www.library.nhs.uk
• http//www.cebm.net/
• http//www.cche.net/usersguides/main.asp
• http//www.healthcare.ubc.ca/calc/clinsig.html

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Summary

• Statistical rigour is important and requires
  careful study
• Medical statistics has advanced enormously and
  for clinical practice EBM/Clinical Epidemiology
  is essential
• Its more important to know how to learn than to
  memorise it all there are fantastic resources
  available on the web these days
• Make sure you understand the central concepts
  around validity no amount of statistics can
  rescue a fatally flawed study
• Always consider the precision of the result
  reported
• Consider whether you need the average effect and
  to what extent you want to particularise a result

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Conclusions

• EBM involves knowledge, skills and attitudes (one
  definition of EBM is Healthcare with Attitude!)
• There are also many summaries of evidence and
  lots of guidelines (NICE SIGN etc) that
  effectively summarise and interpret the evidence
  base
• Learning the skills is helpful for
  individualising care to patients (through
  adjusting the estimates of effect to reflect that
  patients baseline risk)
• Using EBM will help you care for patients more
  effectively, learn from your seniors more
  efficiently and enable your organisation to run
  safely and achieve high quality ratings (were
  judged on how well we support doctors to practice
  EBM)
• It is also a key route into conducting research
• EBM and research are essential to career
  progression these days