SPEX Preventive Medicine 3 — Questions and Answers
Question 1: A cohort study finds that smokers have a relative risk of 15 for lung cancer compared to non-smokers. The prevalence of smoking is 25%. What is the population attributable risk percent (PAR%)?
- Approximately 78% (Correct answer)
- Approximately 65%
- Approximately 50%
- Approximately 88%
Correct answer: Approximately 78%
PAR% = Pe(RR−1)/[Pe(RR−1)+1] × 100 = 0.25×14/(0.25×14+1) × 100 ≈ 78%.
Question 2: Which of the following best describes the hierarchy of controls for occupational hazards, from most to least preferred?
- PPE → administrative → engineering → substitution → elimination
- Elimination → substitution → engineering → administrative → PPE (Correct answer)
- Engineering → elimination → substitution → PPE → administrative
- Administrative → engineering → PPE → substitution → elimination
Correct answer: Elimination → substitution → engineering → administrative → PPE
The hierarchy prioritizes elimination, then substitution, engineering controls, administrative controls, and PPE last.
Question 3: A physician screens 1,000 asymptomatic adults for colorectal cancer using FOBT. 50 test positive; of those, 10 have confirmed cancer. Of the 950 who test negative, 5 have cancer. What is the sensitivity of FOBT in this population?
- 67% (Correct answer)
- 80%
- 20%
- 95%
Correct answer: 67%
Sensitivity = TP/(TP+FN) = 10/(10+5) = 10/15 ≈ 67%.
Question 4: Which foodborne pathogen is most commonly associated with undercooked poultry and is the leading cause of bacterial gastroenteritis in the United States?
- Salmonella enteritidis
- Campylobacter jejuni (Correct answer)
- Listeria monocytogenes
- Clostridium perfringens
Correct answer: Campylobacter jejuni
Campylobacter jejuni is the most frequent cause of bacterial gastroenteritis in the US, typically linked to undercooked poultry.
Question 5: According to ACIP recommendations, which vaccine should be administered as a one-time dose to all adults ≥65 years who have not previously received it?
- Tdap
- High-dose or adjuvanted influenza vaccine
- PCV15 or PCV20 (Correct answer)
- Recombinant zoster vaccine (RZV)
Correct answer: PCV15 or PCV20
ACIP recommends PCV15 or PCV20 as a one-time pneumococcal conjugate vaccine for all immunocompetent adults ≥65.
Question 6: In environmental epidemiology, the unit of analysis in an ecologic study is:
- The individual patient
- A population or group (Correct answer)
- A matched case-control pair
- A clinical cohort
Correct answer: A population or group
Ecologic studies use aggregate data from populations or groups as the unit of analysis rather than individuals.
Question 7: A 45-year-old male construction worker is found to have a blood lead level of 40 µg/dL during routine surveillance. The appropriate OSHA action level for lead that triggers medical surveillance is:
- 10 µg/dL
- 25 µg/dL (Correct answer)
- 40 µg/dL
- 60 µg/dL
Correct answer: 25 µg/dL
OSHA's lead standard requires medical surveillance when blood lead levels are ≥25 µg/dL (action level for medical removal is 50 µg/dL).
SPEX Preventive Medicine 3
A cohort study finds that smokers have a relative risk of 15 for lung cancer compared to non-smokers.
The prevalence of smoking is 25%.
What is the population attributable risk percent (PAR%)?