1. Diagnostic Tests Afshin Ostovar Bushehr University of Medical Sciences Bushehr, 2013 12/7/20151

2. A normal individual is a person; Who has not been sufficiently examined 12/7/20152

3. Introduction It is necessary to distinguish between people in the population who have the disease and those who do not. clinical arena Public health arena How good is the test in separating populations of people with and without the disease in question? 12/7/20153

4. Biologic Variation of Human Populations 12/7/20154 Bimodal curve

5. 12/7/20155 Unimodal curve

6. Validity of screening Tests Sensitivity: o the ability of the test to identify correctly those who have the disease. Specificity: o the ability of the test to identify correctly those who do not have the disease. 12/7/20156

7. Tests with Dichotomous Results 12/7/20157 Gold Standard

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9. False Positive effects Burden on the health care system Labeling effect 12/7/20159

10. False Negative effects Deprivation from effective treatment It depends on: the nature and severity of the disease the effectiveness of available intervention measure Whether the effectiveness is greater if the intervention is administered early in the natural history of the disease 12/7/201510

11. Tests of Continuous Variables 12/7/201511 Sensitivity= 5/20 = 25% Specificity= 18/20 = 90%

12. Tests of Continuous Variables 12/7/201512 Sensitivity= 17/20 = 85% Specificity= 6/20 = 30%

13. Different cut-offs 12/7/201513

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19. Multiple Tests Sequential (Two-stage) Testing Simultaneous (Parallel) Testing 12/7/201519

20. Sequential (Two-stage) Testing 12/7/201520

21. Test 1 Diabetes + _ Test Results + _ 10000 12/7/201521

22. Prevalence = 5% Diabetes + _ Test Results + _ 500950010000 12/7/201522

23. Sensitivity = 70% Diabetes + _ Test Results +350 _150 500950010000 12/7/201523

24. Specificity = 80% Diabetes + _ Test Results +3501900 _1507600 500950010000 12/7/201524

25. Final Result of Test 1 Diabetes + _ Test Results +35019002250 _15076007750 500950010000 12/7/201525

26. Test 2 Diabetes + _ Test Results + _ 35019002250 12/7/201526

27. Sensitivity= 90% Diabetes + _ Test Results +315 _35 35019002250 12/7/201527

28. Specificity=90% Diabetes + _ Test Results +315190 _351710 35019002250 12/7/201528

29. Final Result of two Tests Diabetes + _ Test Results +3151902250 _18593107750 500950010000 12/7/201529 Net sensitivity = 315/500 = 63% Net Specificity = 9310/9600 = 98%

30. Simultaneous Testing 12/7/201530

31. Test A 12/7/201531

32. Test B 12/7/201532

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35. Test A 12/7/201535

36. Test B 12/7/201536

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39. Predictive Value Predictive Value Positive If the test results are positive in this patient, what is the probability that this patient has the disease. Predictive Value Negative If the test results are negative in this patient, what is the probability that this patient do not have the disease 12/7/201539

40. Predictive Value Positive 12/7/201540

41. The predictive value is affected by two factors: o the prevalence of the disease in the population tested o the specificity of the test being used, when the disease is infrequent. 12/7/201541

42. Relationship between Predictive Value and Disease Prevalence 12/7/201542

43. Relationship between Predictive Value and Disease Prevalence 12/7/201543

44. Relationship between Predictive Value and Disease Prevalence 12/7/201544

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47. Relationship between Predictive Value and Specificity 12/7/201547

48. Relationship between Predictive Value and Specificity 12/7/201548

49. Relationship between Predictive Value and Specificity 12/7/201549

50. Relationship between Predictive Value and Specificity 12/7/201550