Example: Coronary Artery Stenosis(Sackett’s text)

• Case/Control studies - 50% prevalence

• What difference if realistic prevalence (e.g., 20% for those where CAS suspected)

• Tests Sensitivity Specificity

  • Exercise ECG .598 .912
  • Radionuclide scan .832 .620

• Criterion: Angiography

• Correlations between the tests

  • When CAS > 70% (Disease “present”) .297
  • When CAS < 70% (Disease “absent”) .135

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