Reference no: EM131195311
Principles of Epidemiology
Questions 14: In planning a casecontrol study of the relationship between smoking and cancer of the cervix, you need to determine if age is a confounder and/or an effect modifier in this relationship. Of 217 cases, 130 are smokers and 198 of the 243 controls are nonsmokers.
The age distribution for cases and controls who are smokers is as follows:
Smokers Age

Cases

Controls

Age 2029

41

6

Age 3039

66

25

Age 40+

23

14

The age distribution for cases and controls who are nonsmokers is as follows:
Nonsmokers Age

Cases

Controls

Age 2029

13

53

Age 3039

37

83

Age 40+

37

62

1. Complete the 2 x 2 table and calculate a crude odds ratio for the casecontrol study relating smoking to cervical cancer. Label the columns& rows and interpret the result.
2. Complete the series of 2 x 2 tables and calculate an odds ratio for each age strata. Label the columns& rows.
3. Is age an effect modifier? Explain your answer.
4. An ageadjusted odds ratio, the MantelHaenszel odds ratio (MHOR), was calculated using the data from the age stratified 2 X 2 tables. The MHOR was 6.3. Compare the crude odds ratio that you calculated in #1 above with this MHOR. Is age a confounder? Explain your answer.
Questions 58: Consider the following events in one man's life. Note that some events are hypothetical and some are real.
Event

Age (years)

Birth

0

Prostate cancer begins

45

Prostate cancer is detectable by screening

50

Man is screened, cancer is detected, and treatment begins

55

If no screening, symptoms would have developed and cancer would have been detected

60

If no screening, death would have occurred

70

Death occurs

85

5. Assume that this man did not get screened. Compute the total preclinical phase of this man's prostate cancer.
6. Assume that this man did not get screened. Compute the total detectable preclinical phase of this man's prostate cancer.
7. Compute the lead time for this patient.
8. Did screening increase the life span of this patient? Justify your answer.
Questions 912: Suppose a new screening test has been developed. The test was evaluated in a probability sample in three communities with the following results:
Mooreville


Health Problem


Present

Absent

Total

Test Result

Positive

887

888

1775

Negative

99

7989

8088


Total

986

8877

9863


Short City


Health Problem


Present

Absent

Total

Test Result

Positive

3634

269

3903

Negative

404

2423

2827


Total

4038

2692

6730


Epiville


Health Problem


Present

Absent

Total

Test Result

Positive

2866

56

2922

Negative

318

506

824


Total

3184

562

3746

9. Calculate the prevalence of the health problem in each of these communities.
10. Calculate and interpret the sensitivity of the test for each community.
11. Calculate and interpret the specificity of the test for each community.
12. Calculate and interpret the predictive value positive for each community.