AT&T; LTE 1:15 AM Test 2.docx QUESTION 27 A new antibody test detects serum anti

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AT&T; LTE 1:15 AM Test 2.docx QUESTION 27 A new antibody test detects serum antibodies against v rus 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? a. Measurement error was introduced into the procedure. b Cases of virus X infection are more severe in the hospital C. Lead time bias occurs among the blood donors d. The prevalence of virus X infection is higher among the hospital patients than among blood donors 2.5 points QUESTION 28 A person with an inapparent infection a is of no epidemiologic importance b. never develops antibodies c. is a danger to family members but not to others in the community d. can transmit the infection to others 2.5 points QUESTION 29 You have just finished administering a food/drink questionnaire to ill and non-ill participants in a Minnesota summer picnic party. The ill individuals developed moderate to severe diarrhea 16 to 46 hours after the picnic. Six persons experienced vomiting. The following data were collected ATE DID NOT EAT Number of people Number of people

Explanation / Answer

28)

Often an acute infection may cause little or no clinical symptoms – the so-called inapparent infection. A well-known example is poliovirus infection: over 90% are without symptoms. During an inapparent infection, sufficient virus replication occurs in the host to induce antiviral antibodies, but not enough to cause disease. Such infections are important for the spread of infection, because they are not easily detected. During the height of the polio epidemic in the US, the quarantine of paralyzed patients had no effect on the spread of the disease, because 99% of the infected individuals had no symptoms and were leading normal lives and spreading infection. Inapparent infections probably are important features of pathogens that are well-adapted to their hosts. They replicate sufficiently to ensure spread to new hosts, but not enough to damage the host and prevent transmission.

So a person with iapperent infection can transmit the infection to others .

He can transmit it to anyone not only family so discarding the third option option 4 is correct

27)

As the specificity and sensitivity is quite high for the test so the best conclusion that can be drawn is that there was some sort of measuremental error..

So the correct option is a

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