DO Preventive Medicine and Public Health 2 — Questions and Answers
Question 1: Herd immunity is achieved when what proportion of a population is immune, preventing sustained transmission of an infectious disease?
- A threshold proportion sufficient to interrupt transmission chains (varies by disease) (Correct answer)
- 100% of the population
- At least 50% of the population regardless of disease
- Only vaccinated individuals, excluding naturally immune
Correct answer: A threshold proportion sufficient to interrupt transmission chains (varies by disease)
Herd immunity thresholds vary by pathogen transmissibility (R0); measles requires ~95% immunity while polio requires ~80–85%.
Question 2: Which dietary pattern is most strongly associated with reduced cardiovascular disease risk in evidence-based medicine?
- Mediterranean diet (rich in fruits, vegetables, whole grains, olive oil, fish) (Correct answer)
- Low-fat diet with unrestricted carbohydrates
- High-protein, low-carbohydrate ketogenic diet
- BRAT diet (bananas, rice, applesauce, toast)
Correct answer: Mediterranean diet (rich in fruits, vegetables, whole grains, olive oil, fish)
The Mediterranean diet has the strongest evidence base for cardiovascular risk reduction, including the landmark PREDIMED trial showing reduced major cardiac events.
Question 3: Which occupational exposure is most strongly linked to mesothelioma?
- Asbestos (Correct answer)
- Silica dust
- Coal dust
- Beryllium
Correct answer: Asbestos
Asbestos exposure is the primary cause of mesothelioma, a malignant tumor of the pleura, peritoneum, or pericardium, with a latency period of 20–50 years.
Question 4: The number needed to treat (NNT) is calculated as:
- 1 / absolute risk reduction (ARR) (Correct answer)
- 1 / relative risk reduction (RRR)
- Event rate in control group minus event rate in treatment group
- Relative risk divided by baseline risk
Correct answer: 1 / absolute risk reduction (ARR)
NNT = 1/ARR; it tells clinicians how many patients must receive treatment for one additional patient to benefit compared to the control condition.
Question 5: USPSTF recommends screening for lung cancer with low-dose CT (LDCT) in adults with what criteria?
- Ages 50–80, 20 pack-year smoking history, current smoker or quit within 15 years (Correct answer)
- Ages 40–75, any tobacco exposure, current smoker only
- Ages 55–80, 30 pack-year history, current smoker only
- All adults over age 45 with any smoking history
Correct answer: Ages 50–80, 20 pack-year smoking history, current smoker or quit within 15 years
The 2021 USPSTF recommendation expanded lung cancer screening to ages 50–80 with ≥20 pack-years who currently smoke or quit within 15 years.
Question 6: Which preventive intervention has the greatest impact on reducing infant mortality in the US?
- Safe sleep practices (back sleeping, firm mattress, no bed-sharing) (Correct answer)
- Routine vitamin K injection at birth
- Early introduction of solid foods
- Neonatal hearing screening
Correct answer: Safe sleep practices (back sleeping, firm mattress, no bed-sharing)
The 'Back to Sleep' campaign (now Safe to Sleep) dramatically reduced SIDS deaths by promoting supine infant sleeping position.
DO Preventive Medicine and Public Health 2
Herd immunity is achieved when what proportion of a population is immune, preventing sustained transmission of an infectious disease?