Characteristics of Diagnostic Tests

1. A new blood test has been developed to identify children with intussusception. A researcher studies this test by comparing the results of this test to a contrast enema. Of the 50 children who have a positive contrast enema, 45 have a positive blood test and 5 have a negative blood test. Of 100 children who have a negative contrast enema, 5 have a positive blood test and 95 have a negative blood test. Identify the following:

sensitivity

specificity

positive predictive value (if these data reflect the prevalence of intussusception)

negative predictive value (if these data reflect the prevalence of intussusception)

likelihood ratio for a positive test

likelihood ratio for a negative test

diagnostic accuracy (if these data reflect the prevalence of intussusception)

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ADVANCED QUESTIONS

positive predictive value (if the prevalence of intussusception is 80%)

positive predictive value (if the prevalence of intussusception is 5%)

negative predictive value (if the prevalence of intussusception is 80%)

negative predictive value (if the prevalence of intussusception is 5%)



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