Epidemiology Quiz 6

A person with an inapparent infection: A.can transmit the infection to others B.is a danger to family members but not to others in the community C.never develops antibodies D.is of no epidemiologic importance

A.can transmit the infection to others

A new screening test for Lyme disease is developed for use in the general population. The sensitivity and specificity of the new test are 60% and 70%, respectively. Three hundred people are screened at a clinic during the first year the new test is implemented. Assume the true prevalence of Lyme disease among clinic attendees is 10%.Calculate the following valueThe predictive value of a positive test is: A.33.0% B.18.2% C.94.0% D.22.2% E.6.0%

B.18.2%

A screening examination was performed on 250 persons for Factor X, which is found in disease Y. A definitive diagnosis for disease Y among the 250 persons had been obtained previously. The results are charted below:The specificity of this test is expressed as: A.30% B.70% C.56% D.7% E.80%

B.70%

A new blood test has been developed to screen for disease Z. Researchers establish 50 units as a cut point above which a test is considered positive and thereby indicative of disease. The test manufacturers determine that the test's sensitivity is unacceptably low. However, the manufacturers are not concerned with the specificity and do not want the cost of the test to rise. How can they improve the sensitivity of the test? A.Test each person's blood twice. B.Lower the cut point below 50 units. C.Raise the cut point above 50 units. D.They cannot improve this test and should begin work developing a new test.

B.Lower the cut point below 50 units

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? A.Measurement error was introduced into the procedure. B.The prevalence of virus X infection is higher among the hospital patients than among blood donors C.Cases of virus X infection are more severe in the hospital D.Lead time bias occurs among the blood donors

B.The prevalence of virus X infection is higher among the hospital patients than among blood donors

A test that determines whether disease is actually present is a: A.screening test B.diagnostic test C.reliability test D.none of the above

B.diagnostic test

An important point about the agent-host-environment model (the epidemiologic triangle) of epidemiologic investigation is that: A.the agent is not as important a factor in disease causality as the host or the environment. B.diseases are multi-causal. C. I.t is necessary that the agent be linked to both the host and the environment and that the agent is present in every case of the disease. D.in order to prove causality, which is a difficult task, the researcher must prove that the agent, host and environmental factors under investigation are both necessary and sufficient to cause the disease being studied.

B.diseases are multi-causal.

Sensitivity and specificity of a screening test refer to its: A.reliability B.validity C.yield D.repeatability E.none of the above

B.validity

An outbreak of salmonellosis occurred after an epidemiology department luncheon, which was attended by 485 faculty and staff. Assume everyone ate the same food items. Sixty-five people had fever and diarrhea, five of these people were severely affected. Subsequent laboratory tests on everyone who attended the luncheon revealed an additional 72 cases.The attack rate of salmonellosis was: A.13.4% B.47.4% C.28.2% D.7.7% E.3.6%

C.28.2% 137/ (137+ 348) X100

What factors comprise the epidemiologic triangle? A.Agent B.Host C.Environment D.All of the above E.A and B only

D.All of the above

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:Which food item appears to be the most probable vehicle for the salmonella (agent) infection associated with the illness? A.Hot dogs B.Hamburgers C.Potato salad D.Ice cream E.Lemonade

D.Ice cream

A screening examination was performed on 250 persons for Factor X, which is found in disease Y. A definitive diagnosis for disease Y among the 250 persons had been obtained previously. The results are charted below:The sensitivity of this test is expressed as: A.30% B.70% C.56% D.7% E.80%

E.80%

A new screening test for Lyme disease is developed for use in the general population. The sensitivity and specificity of the new test are 60% and 70%, respectively. Three hundred people are screened at a clinic during the first year the new test is implemented. Assume the true prevalence of Lyme disease among clinic attendees is 10%.Calculate the following valueThe number of false positives is: A.99 B.9 C.12 D.2,162 E.81

E.81

Which of the following examples involves indirect transmission of disease? A.Malaria B.Hepatitis caused by needle sticks C.HIV/AIDS D.Pneumoconiosis E.A and B

E.A and B

True or False? Antigenicity of an infectious agent is measured by the secondary attack rate.

False

True or False? It is possible for a measure to be valid but unreliable.

False

Attack rate is:

ILL/(ILL+WILL) X 100

True or False? Administration of immune globulin confers passive immunity.

True

True or False? Reliability refers to the ability of a measuring instrument to give consistent results on repeated trials, regardless of its accuracy.

True

True or False? Sensitivity refers to the ability of a screening test to correctly identify all screened individuals who have a disease.

True

True or False? Sexually transmitted diseases, influenza, and acute respiratory infections are examples of conditions transmitted directly (person-to-person).

True

True or False? The case fatality rate of a disease is defined as the number of deaths due to the disease divided by the number of cases of the disease during a specified time period times 100.

True

True or False? The term generation time relates to the time interval between lodgment of an infectious agent in a host and the maximal communicability of the host.

True

True or False? Vaccine preventable diseases include Haemophilus influenzae type b (Hib).

True

True or False? Validity is the ability of a measuring instrument to give a true measure.

True