Statistical knowledge and clinical knowledge
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Transcript Statistical knowledge and clinical knowledge
Statistical knowledge and
clinical knowledge
J. Nummenmaa
M.D. Ph.D.
Knowledge in Medicine -Questions in Medical Epistemology
Evidence-Based Medicine (EBM)
• Ensure availability of reliable research
results for clinicians
–
–
–
–
–
–
How effective treatment?
Research done on patients
Golden standard = Randomised trial
Critical evaluation on research & results
Quality improvement
Decreasing variation
• EBM Guidelines
– Bringing evidence to practice
What is good evidence?
Level A: Consistent Randomised Controlled Clinical Trial,
cohort study, all or none (see note below), clinical
decision rule validated in different populations.
Level B: Consistent Retrospective Cohort, Exploratory
Cohort, Ecological Study, Outcomes Research, casecontrol study; or extrapolations from level A studies.
Level C: Case-series study or extrapolations from level B
studies.
Level D: Expert opinion without explicit critical
appraisal, or based on physiology, bench research or
first principles.
Randomised trial
•
Dr. James Lind 1747
–
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Scurvy prevention
Randomised trial
IS TREATMENT
X MORE EFFECTIVE THAN
•WHOSE
•PREVENTION
CHOICE?
TREATMENT?
DIAGNOSIS
ASOR
CLASSIFICATION
•REPRESENTATIVE
PATIENTS?
Y
IN
THE
TREATMENT
OF DISEASE Z?
•INDUSTRY?
•OBJECTIVES?
ONE
DIAGNOSIS
DOES
NOT EXCLUDE ANOTHER
•RANDOMISATION
ADHERENCE
•WHO
ELSE,
UNIVERSITY?
•DO
ALL
PATIENTS
SHARE
SAME
OBJECTIVES
DIFFERENT
DIAGNOSES
ARE
BASED
ON
•BLINDING
•WHY?
•COMPOSITE
DIFFERENTINDICATORS
CRITERIA
•CO-MORBIDITY
•FINANCIAL
INTERESTS?
N•APPLICABILITY
PATIENTS WITH
Z INDIVIDUAL PATIENTS?
DIAGNOSTIC
DIFFERENCES
ON
•OTHER
FACTORS,
LIFE-STYLE ETC
•SCIENTIFIC
INTERESTS?
IN
HOSPITALS
AND
PRIMARY
CARE
•SIDE-EFFECTS SELECTION
OF
•COMPARING
DIFFERENT
TREATMENTS
INTERNATIONAL
END-POINTS
•MEDICATION
PREVALENCE
AND INCIDENCE HALF TREATED
HALF
TREATED
WITH Y
WITH •SURGERY
XIN HOSPITALS AND PRIMARY CARE
•(PSYCHO)THERAPY
HOW TO CHOOSE
PROBLEMS
ON SOME
•CHOOSING ONE TREATMENT = NOT
CHOOSING
WHAT
PATIENT
OTHER
TREATMENT
TREATMENTS ARE
SELECTION
PROBLEMS
OF
COMPARED?
NUMBER
OF END –POINTS IN DIFFERENT GROUPS
DIAGNOSTIC
CRITERIA
Significance of the data
Statistical significance: p=0.036
•
Risk reduction 30.3%
Out of one hundred patients:
-> 97 remain healthy
-> will get sick whether treated or not
-> one incidence
can be preventedp-value
Statistical
significance:
-> ARR 1% -> NNT= 100
– Propability to get achieved results if null-hypothesis is true
Clinical significance:
Relative risk reduction :percentage
Absolute risk reduction (ARR%)
Number needed to treat (NNT)
Clinical importance
Treating individual patients
Clinically significant risk?
• Cholesterol-lowering medication should be
started if a person, even otherwise healthy,
has a propability of cardiac death higher than
5% / 10 years
– Finnish evidence based (Käypä hoito -)
guidelines for hyperlipidaemia
7
7
To treat or not to treat?
8
To treat or not to treat?
9
9
What to do with myself?
• At the age of 44
• Estimated life-span 88,48
• Intervention: regular exercise + 2-3 doses of
alcohol
• Benefits:
– 0,29 years= 1 600 hours awake
– January - March
– One hour / day= 16 235 hours
– Costs:
• Wine 32 500 €
• Exercise 500 € p.a. = 22 500 €
• Total 55 000 €
– One extra hour of life= 10 hours 34€
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Evidence-Based or Value-Based?
• Comparison of hypertension control between
different countries: 17,5 - 86,4%
• Fahey & Peters: What constitutes controlled hypertension? Patient based
comparison of hypertension guidelines, BMJ, 1996, 313, 7049, 93-96
Recommendations based on same evidence: 50%
/ 50%
• Raine, R & al. Lancet, 2004, 364, 9432, 429-437
• Selection of literature
• Christiaens & al. Scand J Prim Health Care, 2004, 22, 141-145
Evidence-Based or Value-Based?
• 76% of Norwegian men in Trondelage
have higher risk for cardiac diseases
than guidelines recommend
– Cholesterol
– Blood pressure
• How to deal with risks?
– Getz & al 2004
12
Evidence-Based – really?
•
•
•
•
Is data really reliable?
Are the results applicable in practice?
Are the results politically acceptable?
How do the results relate to functioning of the working
group?
• Moreira T (2004): Diversity in clinical guidelines: The role of repertoires
of evaluation. Soc Sci Med 60:1975-1985.
• Value-Based recommendations:
–
–
–
–
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Selection of literature?
Valuation of research methodology?
How effective treatment is effective?
What treatments are favored (Drugs, surgery, therapy)?
13
Hume and EBM Guidelines
• ”…when all of a sudden I am surprised to
find, that instead of the usual
copulations of propositions, is, and is
not, I meet with no proposition that is
not connected with an ought, or an
ought not. This change is imperceptible;
but is however, of the last
consequence.”
– David Hume: A treatise of human nature
(1739)
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General Practitioner
• Treating human beings not
diseases
• Contextuality.
• Networking
• Place of treatment: Clinic,
home
• Understanding meanings
• Resource control
•Continuity
•Openness
•Tolerance and ability to deal
with uncertainty
•Clinical encounter
•Social medicine
•Unselected population
•Patients present with
symptoms
EBM vs GP
• GP
• EBM
– Diagnosis
– Randomised trial
– Interpretation
statistical
– Patient, symptom
– Individual interpretation
– subjetive
– Uncertainty
– ”Objective”
• Limited data
– Uncertainty:
• Lack of knowledge
•
Statistical
significance
• Clinical significance
• Applying knowledge
• Ethics & values
• Limited time
Clinically relevant research?
• University?
• Evidence-Based Guidelines?
– Does not produce new data
– Valuation of research results favours
medical treatment
• Drug industry?
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• GPs themselves?
How does a GP use EBM
Guidelines
• Source of information, as a textbook
• Searching answers for a specific question
• As an institutional quality improvement tool
– Grimshaw ja Eccles in Ridsdale L. (Ed.): Evidence-based practice in
primary care (Churchill Livingstone).