What Happens to the Performance of a Diagnostic Test when the Disease Prevalence and the Cut-Point Change? Pathological scores Healthy scores 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 result NPV = predictive value of a negative test

Pathological scores Healthy scores Healthy population Sick population Cut-point + + − Prevalence Disease + − + Test − Sensitivity 82/100 82% Specificity 275/ % PPV 80/ % NPV 275/ % 25% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + − Prevalence Disease + − + Test − Sensitivity 73/100 73% Specificity 280/ % PPV 73/ % NPV 280/ % 25% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + − Prevalence Disease + − + Test − Sensitivity 70/100 70% Specificity 285/300 95% PPV 70/ % NPV 285/ % 25% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + − Prevalence Disease + − + Test − Sensitivity 63/100 63% Specificity 290/ % PPV 63/ % NPV 290/ % 25% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + − Prevalence Disease + − + Test − Sensitivity 52/100 52% Specificity 300/ % PPV 52/52 100% NPV 300/ % 25% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + − Prevalence Disease + − + Test − Sensitivity 90/100 90% Specificity 255/300 85% PPV 90/ % NPV 255/ % 25% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + − Prevalence Disease + − + Test − Sensitivity 95/100 95% Specificity 234/300 78% PPV 95/161 59% NPV 234/ % 25% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + − Prevalence Disease + − + Test − Sensitivity 100/ % Specificity 195/300 65% PPV 100/ % NPV 195/ % 25%

Pathological scores Healthy scores Healthy population Sick population Cut-point + + Prevalence Disease + − + Test − Sensitivity 49/60 82% Specificity 458/ % PPV 49/ % NPV 458/ % 10% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + Prevalence Disease + − + Test − Sensitivity 44/ % Specificity 467/ % PPV 44/ % NPV 467/ % 10% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + Prevalence Disease + − + Test − Sensitivity 42/60 70% Specificity 475/500 95% PPV 42/ % NPV 475/ % 10% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + Prevalence Disease + − + Test − Sensitivity 38/ % Specificity 485/500 97% PPV 38/ % NPV 485/ % 10% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + Prevalence Disease + − + Test − Sensitivity 31/ % Specificity 500/ % PPV 31/31 100% NPV 500/ % 10% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + Prevalence Disease + − + Test − Sensitivity 54/60 90% Specificity 425/500 85% PPV 54/ % NPV 425/ % 10% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + Prevalence Disease + − + Test − Sensitivity 57/60 95% Specificity 390/500 78% PPV 57/ % NPV 390/ % 10% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + + Prevalence Disease + − + Test − Sensitivity 60/60 100% Specificity 325/500 65% PPV 60/ % NPV 325/ % 10%

Pathological scores Healthy scores Healthy population Sick population Cut-point + − Prevalence Disease + − + Test − Sensitivity 82/100 82% Specificity 92/100 92% PPV 82/90 91% NPV 92/ % 50% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + − Prevalence Disease + − + Test − Sensitivity 73/100 73% Specificity 93/100 93% PPV 73/ % NPV 93/ % 50% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + − Prevalence Disease + − + Test − Sensitivity 70/100 70% Specificity 95/100 95% PPV 70/ % NPV 95/125 76% 50% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + − Prevalence Disease + − + Test − Sensitivity 63/100 63% Specificity 97/100 97% PPV 63/ % NPV 97/ % 50% −

Pathological scores Healthy scores Healthy population Sick population Cut-point − Prevalence Disease + − + Test − Sensitivity 52/100 52% Specificity 100/ % PPV 52/52 100% NPV 100/ % 50% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + − Prevalence Disease + − + Test − Sensitivity 90/100 90% Specificity 85/100 85% PPV 90/ % NPV 85/ % 50% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + − Prevalence Disease + − + Test − Sensitivity 95/100 95% Specificity 78/100 78% PPV 95/ % NPV 78/83 94% 50% −

Pathological scores Healthy scores Healthy population Sick population Cut-point + − Prevalence Disease + − + Test − Sensitivity 100/ % Specificity 65/100 65% PPV 100/135 74% NPV 65/65 100% 50%