3. Section A Diagnosis and Diagnostic Testing

9. Section B Assessment on Diagnostic Testing

21. DIAGNOSTIC ACCURACY OF A TEST Definition The extent to which the results of a diagnostic test reflect true disease status Terminology Accuracy / Validity interchangeable

22. Indicators for assessing diagnostic test

51. Likelihood Ratios and Post-Test Disease Probability

58. Clinical interpretation of post-test probability Disease ruled out Disease ruled in

62. Figure 1a : Likelihood Ratio Nomogram

63. Figure 1b : Likelihood Ratio Nomogram

64. Developmental characteristics: Cut-points and Receiver Operating Characteristic (ROC) Healthy

65. Developmental characteristics: Cut-points and Receiver Operating Characteristic (ROC) Healthy Sick

66. Developmental characteristics: Cut-points and Receiver Operating Characteristic (ROC) Fals pos= 20% True pos=82%

67. Developmental characteristics: Cut-points and Receiver Operating Characteristic (ROC) F pos= 100% T pos=100%

68. Developmental characteristics: Cut-points and Receiver Operating Characteristic (ROC) Fals pos= 9% True pos=70%

69. Developmental characteristics: Cut-points and Receiver Operating Characteristic (ROC) T neg= 100% F neg=100%

70. Developmental characteristics: Cut-points and Receiver Operating Characteristic (ROC) “ F pos + T pos “ is the highest

72. Developmental characteristics: Cut-points and Receiver Operating Characteristic (ROC) Receiver Operating Characteristic (ROC)

73. Developmental characteristics: Cut-points and Receiver Operating Characteristic (ROC) Receiver Operating Characteristic (ROC)

87. Effect of prevalence on predictive value(Se=70%, Sp=90%) 93.0 50,000 Clinical suspicious prostatic nodule 5.6 500 Men, age 75or greater 0.4 35 General population PPV (%) Prevalence (case/100,000) Setting

88. Lead Time 1990 1997 2000 death Diagnosis and treatment Biologic onset of disease 1990 1994 2000 death Biologic onset of disease Screening: diagnosis & treatment

89. Length Bias 1995 2000 death Biologic onset of disease 1989 1994 death Biologic onset of disease Screening: diagnosis & treatment 2002 1994 Screening:

90. Thanks!!!