A new antibody test detects serum antibodies against virus X…
A new antibody test detects serum antibodies against virus X (sensitivity 99%, specificity 90%). When applied in a group of hospitalized patients diagnosed as having virus X infections, the test is found to have a positive predictive value of 85%. When used to screen a group of healthy blood donors for virus X infections, the test is found to have a positive predictive value of 30%. Which of the following best explains this difference between the positive predictive values?
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