Case Study
1. 6,750 people who were free of disease X were enrolled in a cohort study in 1985 and followed with annual exams and interviews through 1995. Exposure to factor A was determined at study enrollment and the participants were followed until 1995 to observe new cases of disease X. Data from the study at the end of follow-up are shown in the following table. What is the incidence rate of disease X among persons exposed to factor A?
Exposure to Factor A
People with Disease X
People without Disease X
Not Exposed
30
3,720
Exposed
120
2,880
Select one:
a. 0.04
b. 0.19
c. 0.25
d. 4.00
e. 5.17
2. A disease has an incidence of 10 per 1,000 persons per year, and 80% of those affected will die within 1 year. Prior to the year 2000, only 50% of cases of the disease were detected by physician diagnosis prior to death. In the year 2000, a lab test was developed that identified 90% of cases an average of 6 months prior to symptom onset; however, the prognosis did not improve after diagnosis. Comparing the epidemiology of the disease prior to 2000 with the epidemiology of the disease after the development of the lab test, which statement is true concerning the disease in 2000?
Select one:
a. Incidence is higher and prevalence is higher than in 1999
b. Incidence is higher in 2000 but prevalence remains the same
c. Incidence is the same in 2000 but prevalence is higher than in 1999
d. Both incidence and prevalence remain the same as in 1999
e. Incidence is the same in 2000 but prevalence is lower than in 1999
3. A disease has an incidence of 10 per 1,000 persons per year, and 80% of those affected will die within 1 year. Prior to the year 2000, only 50% of cases of the disease were detected by physician diagnosis prior to death. In the year 2000, a lab test was developed that identified 90% of cases an average of 6 months prior to symptom onset; however, the prognosis did not improve after diagnosis. Which statement is true concerning the duration of the disease after the development of the lab test?
Select one:
a. Mean duration of a case of the disease is shorter in 2000
b. Mean duration of a case of the disease is the same in 2000
c. Mean duration of a case of the disease is longer in 2000
d. No inference about mean duration can be made since the lab test has only been available for 1 year
4. A disease has an incidence of 10 per 1,000 persons per year, and 80% of those affected will die within 1 year. Prior to the year 2000, only 50% of cases of the disease were detected by physician diagnosis prior to death. In the year 2000, a lab test was developed that identified 90% of cases an average of 6 months prior to symptom onset; however, the prognosis did not improve after diagnosis. Which statement is true concerning the disease-specific mortality rate after the development of the lab test?
Select one:
a. The mortality rate for the disease is decreased in 2000
b. The mortality rate for the disease is the same in 2000
c. The mortality rate for the disease is increased in 2000
d. No inference about the mortality rate can be made since the lab test has only been available for 1 year
5. A group of researchers are interested in conducting a clinical trial to determine whether a new cholesterol-lowering agent was useful in preventing coronary heart disease (CHD). They identified 14,327 potential participants for the trial. At the initial clinical exam, 422 were discovered to have CHD. The remaining subjects entered the trial and were divided equally into the treatment and placebo groups. Of those in the treatment group, 535 developed CHD after 5 years of follow-up while 568 developed CHD during the same period in the placebo group. What was the prevalence of CHD at the initial exam?
Select one:
a. 10.4 per 1,000 persons
b. 18.7 per 1,000 persons
c. 29.5 per 1,000 persons
d. 47.3 per 1,000 persons
e. 79.3 per 1,000 persons
