Project Part 2 Descriptions

1. Project Part 2
Section 1 - Group 1
There were a total of 58 firefighters in 2 fire departments.
A case was either a probable or confirmed case of cryptosporidiosis. A clinical
case was defined as diarrhea (three or more loose stools in a 24-hour period) or
gastrointestinal illness (four or more symptoms [e.g., abdominal cramps, nausea,
vomiting, or fever]) in a person within 12 days after the fire response. A
confirmed case was defined as a clinical case with Cryptosporidium organisms
detected in stool, intestinal fluid, or tissue samples; antigens in stool or
intestinal fluid; or nucleic acid in stool. A probable case was defined as a
clinical case that lacked positive laboratory confirmation but was linked
epidemiologically to a confirmed case. Contact with pond water was defined as
washing or cooling off with the pond water.
Of these, 23 firefighters met the case definition for cryptosporidiosis. You were
able to interview 54 firefighters who were at the barn fire. The results of your
retrospective cohort are below.
Exposure Case Total Non-case Total
Calves at farm 7 15 16 39
Fire department 1 9 17 14 37
Fire department 2 14 37 9 17
Drinking cooler water 6 12 17 42
Drinking bottled water 4 34 19 20
Drinking/contact with pond water 19 28 4 26
1. Calculate the attack rate (in percent rounded to the tenths place) for the
exposed and unexposed groups.
2. Calculate the measure of association and 95% confidence interval for each
exposure. Which of these exposures most likely caused the outbreak? Give 2
reasons to justify your conclusion.
3. What additional questions might you have about this investigation that could
inform your discussion and recommendations?

2. Project Part 2
Section 1 - Group 2
To investigate the association, you have decided to use the data from a prospective
community cohort in Clayton, Ohio (population 238,178). The Clayton Cancer Study
enrolled 123,456 adults that have been followed since 1993. In 2001, the Clayton
Cancer Study began collecting exposure data on electronic cigarette use. For
efficiency, you use a nested case-control approach. Data from all cases of lung
cancer are used. For comparison, 3 controls per case are selected of comparable
age. The results are below.
Men Case Control
Electronic cigarette only 43 102
Tobacco cigarettes only 378 264
Electronic and tobacco cigarettes 231 189
Neither electronic nor tobacco cigarettes 337 2412
989 2967
Women Case Control
Electronic cigarette only 19 43
Tobacco cigarettes only 78 41
Electronic and tobacco cigarettes 72 109
Neither electronic nor tobacco cigarettes 64 506
233 699
1. What is the exposure rate of electronic cigarettes in your study among men and
women? What proportion of your cohort experienced lung cancer?
2. Calculate the measure of association and a 95% confidence interval for each
exposure for men, women, and both combined.
3. Are electronic cigarettes related to lung cancer? Are they more or less
harmful than tobacco cigarettes?
4. What additional questions might you have about this nested case-control study
that could inform your discussion and recommendations?

3. Project Part 2
Section 1 - Group 3
You conduct a cross sectional telephone survey of a representative sample of 627
refugees. The survey asked about demographics, mental health history, difficulties
after arrival in the United States, perceived level of social support, current
symptoms of posttraumatic stress disorder (PTSD) and traumatic experiences, and
symptoms of anxiety, depression and psychological distress. Participants were asked
if they had ever expressed suicidal ideation (i.e., ever thought seriously about
committing suicide in their lifetimes). Assume there is no confounding by state of
residence, age, and sex.
Suicidal ideation
(N=52)
No suicidal ideation
(N=575)
Exposure n (%) n (%)
Pre-migration experience
Home or shelter fire 29 82
Violent crime 13 102
Post-migration experience
Unable to find work 22 226
Poor access to counseling services 34 45
Social isolation 16 189
Little help from government 22 193
Separation from family 23 39
1. What is the measure of association for your study? Calculate the percent
exposure, measure of association, and 95% confidence interval for each potential
risk factor.
2. Which pre-migration experience is more likely to be associated with suicidal
ideation? Which of the post-migration experiences could provide the greatest
opportunity for public health intervention?
3. What additional questions might you have about this investigation that could
inform your discussion and recommendations?

4. Project Part 2
Section 1 - Group 4
You enrolled volunteers from 11 drug-treatment clinics in New York, New York in a
randomized, double-blind, placebo-controlled trial. Participants were eligible if
they were aged 18–50 years, were HIV-negative, and reported injecting drugs during
the previous year. You randomly assigned participants to either tenofovir or
placebo. There were 3125 participants followed from 2009 through 2013. Of these,
you assigned 1559 to tenofovir and 1566 to placebo. There were no significant
differences in demographic characteristics or behaviors between the two arms of the
trial. There were 66 incident HIV infections in the placebo group (observed for a
total of 4734 person-years) and 41 infections in the tenofovir group (observed for
a total of 4765 person-years). The results of the study by 6 months of observation
are below.
Placebo N=1566 Tenofovir N=1559
t (month) lt dt t (month) lt dt
6 1534 4 6 1502 3
12 1434 7 12 1439 4
18 1124 6 18 1178 4
24 1009 8 24 1072 3
30 945 11 30 966 2
36 887 4 36 803 2
42 618 6 42 616 4
48 597 5 48 578 3
48 520 5 48 502 6
54 456 7 54 497 4
60 344 3 60 376 6
Total 66 Total 41
1. What is the rate of incident HIV infection in the placebo group and in the
tenofovir group? What is the cumulative risk of HIV infection in the
placebo group and in the tenofovir group?
2. What is the relative measure of association that describes the effect of
tenofovir compared to placeobo?
3. What additional questions might you have about this trial that could
inform your discussion and recommendations?

5. Project Part 2
Section 1 - Group 5
You conduct a case-control study by abstracting prenatal records from the 23
anencephalic-affected pregnancies and 92 randomly selected control subject
pregnancies in women who had received care at the same prenatal clinics. Control
subjects were matched to case-patients by the month and year of last menstrual
period. Eligibility criteria for control subjects included a pregnancy without an
indication of a structural or genetic birth defect during routine prenatal care and
prenatal residence in one of the three study counties.
Case Control
Age
18-24 4 18
25-29 5 25
30-34 9 38
35-39 3 6
40+ 2 5
History of fetal loss 4 19
Current smoker 8 27
Alcohol use
None 11 45
Moderate 7 33
Heavy 5 14
Vitamin supplement use* 12 66
Pregnancy health condition** 4 18
Well water consumption 16 11
Total 23 92
* Includes folic acid supplementation
** Anemia, diabetes, or infectious diseases
4. Calculate the measure of association and 95% confidence interval for each
exposure.
5. Which of these exposures most likely caused the increase in anencephaly? Give 2
reasons to justify your conclusion.
6. What additional questions might you have about this investigation that could
inform your discussion and recommendations?