Population Health and Epidemiology Flashcards

A case-control study reports an odds ratio of 3.2 for smoking and a rare disease. What does this odds ratio best approximate?

Answer: The relative risk of the disease

For rare diseases the odds ratio closely approximates the relative risk because the disease odds approximate the disease risk.

A new screening test has high sensitivity but low specificity. What is the most likely consequence in a low-prevalence population?

Answer: Many false positives

Low specificity combined with low disease prevalence generates a large number of false-positive results.

Which measure quantifies the proportion of disease in exposed individuals attributable to the exposure?

Answer: Attributable risk (risk difference)

Attributable risk is the difference in risk between exposed and unexposed groups, reflecting excess risk due to exposure.

In a randomised controlled trial, allocation concealment primarily protects against which bias?

Answer: Selection bias

Allocation concealment prevents foreknowledge of group assignment, reducing selection bias at enrolment.

A study finds an association between coffee drinking and lung cancer, but smoking is more common among coffee drinkers. Smoking is best described as a:

Answer: Confounder

Smoking is associated with both the exposure and the outcome and is not on the causal pathway, making it a confounder.

The basic reproduction number (R0) of a measles outbreak is 15. Approximately what herd immunity threshold is required to halt transmission?

Answer: About 93%

The herd immunity threshold equals 1 minus 1/R0, which for R0 of 15 is roughly 93%.

Which study design is most appropriate to estimate the prevalence of obesity in a community at a single point in time?

Answer: Cross-sectional survey

A cross-sectional survey measures exposure and outcome simultaneously, making it ideal for prevalence estimation.