Deck 11: Screening for Disease in the Community

Question 1

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

Answer 1

True

Question 2

Validity is the ability of a measuring instrument to give a true measure.

Answer 2

True

Question 3

It is possible for a measure to be valid but unreliable.

Answer 3

False

Question 4

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

Question 5

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

Question 6

Sensitivity and specificity of a screening test refer to its:

A) reliability.
B) validity.
C) yield.
D) repeatability.
E) None of these is correct.

Question 7

Figure 11-12 represents different combinations and qualities of validity and reliability (high vs. low). Which set of symbols represents high validity?

A) A
B) B
C) C
D) Both A and C
E) None of these is correct.

Question 8

Figure 11-12 represents different combinations and qualities of validity and reliability (high vs. low). Which set of symbols represents high reliability?

A) A
B) B
C) C
D) Both A and C
E) None of these is correct.

Question 9

Figure 11-12 represents different combinations and qualities of validity and reliability (high vs. low). Which set of symbols represents low reliability?

A) A
B) B
C) C
D) Both A and C
E) None of these is correct.

Question 10

Figure 11-12 represents different combinations and qualities of validity and reliability (high vs. low). Which set of symbols represents high validity but low reliability?

A) A
B) B
C) C
D) Both A and C
E) None of these is correct.

Question 11

A test developed to assess age-related changes in bone density that does not pick up these changes has:

A) low predictive validity.
B) low concurrent validity.
C) low construct validity.
D) None of these is correct.

Question 12

The degree of agreement among several trained experts refers to:

A) internal consistency.
B) repeated measures.
C) concurrent validity.
D) interjudge reliability.
E) both internal consistency and concurrent validity.

Question 13

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

A) screening test.
B) diagnostic test.
C) reliability test.
D) None of these is correct.
E) validity test.

Question 14

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?

A) Selective screening
B) Mass screening
C) Ad hoc screening
D) Multiphasic screening
E) Opportunistic screening

Question 15

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 here:
The sensitivity of this test is expressed as:

A) 30%.
B) 70%.
C) 56%.
D) 7%.
E) 80%.

Question 16

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 here:
The specificity of this test is expressed as:

A) 30%.
B) 70%.
C) 56%.
D) 7%.
E) 80%.

Question 17

Lead time bias is best described as:

A) an apparently lower survival rate among persons screened compared to an unscreened group.
B) an actually longer survival time for persons identified during a screening program because they were given an effective treatment.
C) a similar survival time for persons identified during a screening program relative to persons who are diagnosed by clinical symptoms.
D) an apparently longer survival time among persons identified during a screening program because they were identified at an earlier stage of their disease.

Question 18

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.

Question 19

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 they 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.

Question 20

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

A) 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
B) Increasing the number of persons who are classified as abnormal and unnecessarily subjecting people to potential risks associated with diagnostic procedures
C) Overreferral of persons without disease for diagnosis and failure to identify persons who have the condition
D) Failure to identify persons who have the condition
E) Failure to identify persons who have the condition, increasing the number of persons who are classified as abnormal, overreferral of persons without disease for diagnosis, and unnecessarily subjecting people to potential risks associated with diagnostic procedures

Question 21

Which of the following conditions are favorable to population screening for presymptomatic diagnosis of a given disease?

A) A relatively high prevalence of the disease, availability of effective treatment, and a screening test with a high degree of sensitivity
B) A screening test with a high degree of sensitivity and a relatively high prevalence of the disease
C) Availability of effective treatment and availability of physicians to perform the screening test procedure
D) Availability of physicians to perform the screening test procedure
E) Availability of physicians to perform the screening test procedure, a screening test with a high degree of sensitivity, availability of effective treatment, and a relatively high prevalence of the disease

Question 22

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:

A) 33.0%.
B) 18.2%.
C) 94.0%.
D) 22.2%.
E) 6.0%.

Question 23

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 number of false positives is:

A) 99.
B) 9.
C) 12.
D) 2162.
E) 81.

Question 24

Cataracts of the eye may be difficult to diagnose, especially in the early stages. In a study of the reliability of their diagnoses, two physicians each examined the same 1000 eyes, without knowing the other's diagnoses. Each physician found 100 eyes with cataracts. Does this mean that the diagnoses are reliable? Please provide a short answer explaining your position.