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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%