Statistical knowledge and clinical knowledge
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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

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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

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

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, case-control 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

Randomised trial

  • Dr. James Lind 1747

    • Scurvy prevention


Randomised trial1

IS TREATMENT X MORE EFFECTIVE THAN Y IN THE TREATMENT OF DISEASE Z?

N PATIENTS WITH Z

Randomised trial

HALF TREATED WITH Y

HALF TREATED WITH X

  • WHOSE CHOICE?

    • INDUSTRY?

    • WHO ELSE, UNIVERSITY?

  • WHY?

    • FINANCIAL INTERESTS?

    • SCIENTIFIC INTERESTS?

  • COMPARING DIFFERENT TREATMENTS

    • MEDICATION

    • SURGERY

    • (PSYCHO)THERAPY

  • CHOOSING ONE TREATMENT = NOT CHOOSING SOME OTHER TREATMENT

  • PREVENTION OR TREATMENT?

  • OBJECTIVES?

    • DO ALL PATIENTS SHARE SAME OBJECTIVES

  • COMPOSITE INDICATORS

    • APPLICABILITY ON INDIVIDUAL PATIENTS?

  • SIDE-EFFECTS

  • DIAGNOSIS AS CLASSIFICATION

    • ONE DIAGNOSIS DOES NOT EXCLUDE ANOTHER

    • DIFFERENT DIAGNOSES ARE BASED ON DIFFERENT CRITERIA

  • DIAGNOSTIC DIFFERENCES

    • IN HOSPITALS AND PRIMARY CARE

    • INTERNATIONAL

  • PREVALENCE AND INCIDENCE

    • IN HOSPITALS AND PRIMARY CARE

  • REPRESENTATIVE PATIENTS?

  • RANDOMISATION

  • BLINDING

  • CO-MORBIDITY

  • OTHER FACTORS, LIFE-STYLE ETC

ADHERENCE

NUMBER OF END –POINTS IN DIFFERENT GROUPS

SELECTION OF END-POINTS

HOW TO CHOOSE WHAT TREATMENTS ARE COMPARED?

PROBLEMS ON PATIENT SELECTION

PROBLEMS OF DIAGNOSTIC CRITERIA


Significance of the data

Significance of the data

Statistical significance: p=0.036

Riskreduction 30.3%

Out of onehundredpatients:

-> 97 remainhealthy

-> willgetsickwhethertreatedornot

-> oneincidencecanbeprevented

-> ARR 1% -> NNT= 100

  • Statistical significance: p-value

    • Propability to get achieved results if null-hypothesis is true

  • Clinicalsignificance:

  • Relativeriskreduction :percentage

  • Absoluteriskreduction (ARR%)

  • Numberneeded to treat (NNT)

  • Clinicalimportance

    • Treatingindividualpatients


Clinically significant risk

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


To treat or not to treat

To treat or not to treat?


To treat or not to treat1

To treat or not to treat?

9


What to do with myself

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€

10


Evidence based or value based

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 based1

    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


    Evidence based really

    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:

    • Selection of literature?

    • Valuation of research methodology?

    • How effective treatment is effective?

    • What treatments are favored (Drugs, surgery, therapy)?

  • 13


    Hume and ebm guidelines

    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)

    14


    General practitioner

    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

    • Clinicalencounter

    • Social medicine

    • Unselectedpopulation

    • Patientspresent with symptoms


    Ebm vs gp

    EBM

    Diagnosis

    Randomised trial

    Interpretation statistical

    ”Objective”

    Uncertainty:

    Statistical significance

    Clinical significance

    GP

    Patient, symptom

    Individual interpretation

    subjetive

    Uncertainty

    Limited data

    Lack of knowledge

    Applying knowledge

    Ethics & values

    Limited time

    EBM vs GP


    Clinically relevant research

    Clinically relevant research?

    • University?

    • Evidence-Based Guidelines?

      • Does not produce new data

      • Valuation of research results favours medical treatment

    • Drug industry?

    • GPs themselves?


    How does a gp use ebm guidelines

    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).


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