what happens to the performance of a diagnostic test when the disease prevalence and the cut-point...
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What Happens to the Performance of a Diagnostic Test when the Disease Prevalence and the Cut-Point Change?
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point- +
Click on the + or –to shift the cut-point
+
-
Prevalence
Click on the + or –to alter the prevalence
Remember: PPV = predictive value of a positive test resultNPV = predictive value of a negative test
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
−
Prevalence
Disease + −
+Test −
25
275
82
18
Sensitivity 82/100 82%
Specificity 275/300 91.7%
PPV 80/107 74.8%
NPV 275/295 93.2%
25%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
−
Prevalence
Disease + −
+Test −
20
280
73
27
Sensitivity 73/100 73%
Specificity 280/300 93.3%
PPV 73/93 78.5%
NPV 280/307 91.2%
25%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
−
Prevalence
Disease + −
+Test −
15
285
70
30
Sensitivity 70/100 70%
Specificity 285/300 95%
PPV 70/85 82.4%
NPV 285/315 90.5%
25%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
−
Prevalence
Disease + −
+Test −
10
290
63
37
Sensitivity 63/100 63%
Specificity 290/300 96.7%
PPV 63/70 86.3%
NPV 290/327 88.7%
25%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point
+
−
Prevalence
Disease + −
+Test −
0
300
52
48
Sensitivity 52/100 52%
Specificity 300/300 100%
PPV 52/52 100%
NPV 300/348 86.2%
25%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
−
Prevalence
Disease + −
+Test −
45
255
90
10
Sensitivity 90/100 90%
Specificity 255/300 85%
PPV 90/135 66.7%
NPV 255/265 96.2%
25%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
−
Prevalence
Disease + −
+Test −
66
234
95
5
Sensitivity 95/100 95%
Specificity 234/300 78%
PPV 95/161 59%
NPV 234/239 97.9%
25%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
−
Prevalence
Disease + −
+Test −
105
195
100
0
Sensitivity 100/100 100%
Specificity 195/300 65%
PPV 100/205 48.8%
NPV 195/195 100%
25%
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
Prevalence
Disease + −
+Test −
42
458
49
11
Sensitivity 49/60 82%
Specificity 458/500 91.6%
PPV 49/91 53.8%
NPV 458/469 97.7%
10%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
Prevalence
Disease + −
+Test −
33
467
44
16
Sensitivity 44/60 73.3%
Specificity 467/500 93.4%
PPV 44/77 57.1%
NPV 467/483 96.9%
10%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
Prevalence
Disease + −
+Test −
25
475
42
18
Sensitivity 42/60 70%
Specificity 475/500 95%
PPV 42/67 62.7%
NPV 475/493 96.4%
10%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
Prevalence
Disease + −
+Test −
15
485
38
22
Sensitivity 38/60 63.3%
Specificity 485/500 97%
PPV 38/53 71.7%
NPV 485/506 95.8%
10%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point
+
Prevalence
Disease + −
+Test −
0
500
31
29
Sensitivity 31/60 51.7%
Specificity 500/500 100%
PPV 31/31 100%
NPV 500/529 94.5%
10%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
Prevalence
Disease + −
+Test −
75
425
54
6
Sensitivity 54/60 90%
Specificity 425/500 85%
PPV 54/129 41.9%
NPV 425/431 98.6%
10%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
Prevalence
Disease + −
+Test −
110
390
57
3
Sensitivity 57/60 95%
Specificity 390/500 78%
PPV 57/167 34.1%
NPV 390/393 99.2%
10%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
+
Prevalence
Disease + −
+Test −
175
325
60
0
Sensitivity 60/60 100%
Specificity 325/500 65%
PPV 60/235 25.5%
NPV 325/325 100%
10%
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
−
Prevalence
Disease + −
+Test −
8
92
82
18
Sensitivity 82/100 82%
Specificity 92/100 92%
PPV 82/90 91%
NPV 92/110 83.6%
50%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
−
Prevalence
Disease + −
+Test −
7
93
73
27
Sensitivity 73/100 73%
Specificity 93/100 93%
PPV 73/80 91.3%
NPV 93/120 77.5%
50%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
−
Prevalence
Disease + −
+Test −
5
95
70
30
Sensitivity 70/100 70%
Specificity 95/100 95%
PPV 70/75 93.3%
NPV 95/125 76%
50%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
−
Prevalence
Disease + −
+Test −
3
97
63
37
Sensitivity 63/100 63%
Specificity 97/100 97%
PPV 63/66 95.5%
NPV 97/134 72.4%
50%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point
−
Prevalence
Disease + −
+Test −
0
100
52
48
Sensitivity 52/100 52%
Specificity 100/100 100%
PPV 52/52 100%
NPV 100/148 67.6%
50%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
−
Prevalence
Disease + −
+Test −
15
85
90
10
Sensitivity 90/100 90%
Specificity 85/100 85%
PPV 90/105 85.7%
NPV 85/95 89.5%
50%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
−
Prevalence
Disease + −
+Test −
22
78
95
5
Sensitivity 95/100 95%
Specificity 78/100 78%
PPV 95/117 81.2%
NPV 78/83 94%
50%
−
Pathologicalscores
Healthyscores
Healthy population
Sick population
Cut-point+
−
Prevalence
Disease + −
+Test −
35
65
100
0
Sensitivity 100/100 100%
Specificity 65/100 65%
PPV 100/135 74%
NPV 65/65 100%
50%