UTK PUBH 202 Ch.8&11 Quiz

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%.) The predictive value of a positive test is:

18.2%

To test the efficacy of a health education program in reducing the risk of foodborne and waterborne diseases, the residents of two Peruvian villages were given an intensive health education program. At the end of two years, the incidence rates of important waterborne and foodborne diseases in these villages were compared with those in two similar control villages without any education program. Which of the following study designs most appropriately characterizes this situation?

Community trial

T or F: A therapeutic trial involves the study of the effectiveness of a substance or program to prevent disease.

False

T or F: External validity is not connected with the selection of sample subjects.

False

The physical examination records of the incoming freshman class of 1935 at the University of Minnesota are examined in 1980 to see whether their recorded height and weight at the time of admission to the university are related to their chance of developing coronary heart disease by 1981. Which of the following study designs most appropriately characterizes this situation?

Historical prospective cohort study

Drs. Poke and Jab conducted an employee health program that used five screening tests at the same time to detect several diseases among workers. Which type of program is this?

Multiphasic screening

The entire population of a given community is examined, and all who are judged to be free from bowel cancer are questioned extensively about their diets. These people then are followed for several years to see whether their eating habits will predict their risk of developing bowel cancer. Which of the following study designs most appropriately characterizes this situation?

Prospective cohort study

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?

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

T or F: Clinical trials enroll individual subjects and enable randomization of subjects to receive or not receive the intervention.

True

T or F: Reliability refers to the ability of a measuring instrument to give consistent results on repeated trials, regardless of its accuracy.

True

T or F: Sensitivity refers to the ability of a screening test to correctly identify all screened individuals who have a disease.

True

T or F: Specificity refers to the ability of a screening test to identify only nondiseased individuals who actually do not have the disease.

True

Which of the following are the adverse consequences of using a screening test that has a low specificity?

Unnecessarily subjecting people to potential risks associated with diagnostic procedures, overreferral of persons without disease for diagnosis, and increasing the number of persons who are classified as abnormal

A test that determines whether disease is actually present is a:

diagnostic test.

A major advantage of community trials is that they are able to:

estimate directly the realistic impact of behavior change.

Controlled clinical trials enable researchers to:

test new drugs, new therapies, and new medical devices. exercise control over who will receive an exposure. identify definitive relationships between causes and effects. All are correct.

In contrast to observational studies, intervention studies are employed to:

test the efficacy of prevention measures.

The purpose of a double-blind design in clinical trials is to reduce error that results from:

the way in which the outcome is assessed and subjects' knowledge of their assignment to study conditions.