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Costeffectiveness of Screening Tests Mark Hlatky, MD Stanford University

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Goal is to find disease 'early' when it is simpler to treat. Best ... Mammography. CEA of Screening Tests. Cost-effectiveness measures 'value for money spent' ... – PowerPoint PPT presentation

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Title: Costeffectiveness of Screening Tests Mark Hlatky, MD Stanford University


1
Cost-effectiveness of Screening Tests Mark
Hlatky, MDStanford University

2
Screening Principles
  • Goal is to find disease early when it is
    simpler to treat
  • Best examples are in cancer
  • Value of screening program depends on
  • Disease characteristics
  • Test performance, cost
  • Treatments available for identified disease

3
Screening Principles Disease
  • Disease to be screened should be
  • Serious - irreversible effects
  • Prevalence is high in target population
  • Natural history allows early detection
  • t 0 t 1
    t 2
  • 1st Develops 1st Detectable
    1st Symptoms
  • t 2 t 1 should be long for effective
    screening

4
Screening Principles Test
  • Good screening test is
  • Sensitive AND specific to detect disease OR
  • Separates high and low risk to develop disease
  • Acceptable to patients
  • Safe
  • Cheap

5
Screening Principles Therapy
  • Effective therapy available
  • For affected patient
  • To avoid spread of disease
  • Therapy should be either better or cheaper when
    given early

6
CEA of Screening Tests
  • Cost-effectiveness has examined therapies
  • Bypass surgery for angina
  • Statins for high cholesterol
  • Therapies have direct effect on outcome
  • CE weighs improvement in outcome against increase
    in cost
  • Screening tests provide information
  • Indirect effects on outcome
  • CE of tests is more difficult to judge, since it
    depends on how test results are used to change
    therapy

7
Screening Tests Cost
  • Total costs include the cost of
  • Test itself
  • Follow-up tests
  • Subsequent treatment
  • Complications of tests, therapy

8
Screening Tests Effectiveness
  • Direct health benefits minor
  • Low risk or absence of disease is reassuring, but
  • Labelling can be harmful
  • Most benefits are due to changing therapy
  • Adding effective drugs
  • Potential value of positive test in improving
    adherence to preventive therapy
  • But EBCT results didnt change patient behavior
    in the PACC randomized trial

JAMA 2003 289 2215-2223.
9
Screening Tests Incremental Information
  • Information from test may be redundant or
    available more simply, cheaply
  • Clinical history very useful for CHD risk
  • Framingham risk score
  • Alternative tests
  • Imaging, biomarkers, genetic tests of risk?
  • Cost-effectiveness always compares 2 or more
    alternatives

10
Tests and Treatment Thresholds
  • Prototype decision is to
  • Treat without testing
  • Test, treat if positive
  • No treatment, no test
  • Optimal strategy depends on
  • Pretest probability or risk
  • Test sensitivity/specificity or relative risk of
    test results
  • Effectiveness of treatment

11
Tests and Treatment Thresholds
  • Optimal strategy is
  • Low probability/risk -- no therapy, no test
  • Intermediate probability/risk test, treat if
    results positive
  • High probability/risk treat w/o testing

Neither
Test
Treat
High
Low
N Engl J Med. 19803021109-17
12
Diagnostic Test Evaluation
  • Case series usual source of information
  • Correlation with gold standard
  • Prediction of prognosis
  • Randomized studies of tests are unusual
  • Invasive vs conservative evaluation strategies
    post-MI
  • BNP testing of pts with acute dypnea
  • Mammography

13
CEA of Screening Tests
  • Cost-effectiveness measures value for money
    spent
  • Costs include follow-up tests therapy
  • Effectiveness measure is outcome
  • Test gives information
  • Effect on outcome is indirect
  • Evaluation must consider value compared with
  • Clinical history
  • Other tests
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