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First create a table of the test results considering that a contrast enema is the criterion ("gold") standard. In other words, a patient with a positive contrast enema is considered to truly have intussusception and a patient with a negative contrast enema is considered to truly not have intussusception. So, the resulting table is:


 * =  ||= Patients with the Disease ||= Patients without the Disease ||= Total ||
 * = Test Positive ||= 45 ||= 5 ||= 50 ||
 * = Test Negative ||= 5 ||= 95 ||= 100 ||
 * = Total ||= 50 ||= 100 ||= 150 ||

Sensitivity = 45/50 = 0.90 = 90% (results from the left column)

Specificity = 95/100 = 0.95 = 95% (results from the right column)

Positive Predictive Value = 45/50 = 0.90 = 90% (results from the top row)

Negative Predictive Value = 95/100 = 0.95 = 95% (results from the bottom row)

Likelihood ratio for a positive test = sensitivity/(1-specificity) = 0.90/(1-0.95) = 0.90/0.05 = 18

Likelihood ratio for a negative test = (1-sensitivity)/specificity = (1-0.90)/0.95 = 0.1/0.95 = 0.11

Diagnostic accuracy = (45 + 95) / 150 = 140/150 = 0.933 = 93.3%