Population Health and Epidemiology Flashcards

Lead-time bias most commonly causes screening programs to falsely appear to:

Answer: Improve survival time

Earlier detection lengthens the apparent survival from diagnosis without changing the actual time of death.

A relative risk of 1.0 with a 95% confidence interval of 0.85 to 1.18 indicates the association is:

Answer: Not statistically significant

A confidence interval crossing 1.0 means the result is not statistically significant.

Which of the following is a notifiable disease that doctors in Australia are legally required to report to public health authorities?

Answer: Tuberculosis

Tuberculosis is a nationally notifiable communicable disease requiring mandatory reporting.

The incidence of a disease is 5 new cases per 1000 person-years and the average duration is 4 years. What is the approximate prevalence?

Answer: About 20 per 1000

Prevalence approximately equals incidence multiplied by duration, giving 5 × 4 = 20 per 1000.

Which bias arises when cases recall past exposures more thoroughly than controls in a case-control study?

Answer: Recall bias

Recall bias occurs because people with disease often remember exposures differently than healthy controls.

A vaccine trial reports a relative risk reduction of 80%. If the unvaccinated risk is 10%, what is the absolute risk reduction?

Answer: 8 percentage points

Absolute risk reduction equals relative risk reduction times baseline risk, so 0.80 × 10% = 8%.

Which level of disease prevention does cervical cancer screening with Pap testing represent?

Answer: Secondary prevention

Screening detects disease at an early or pre-clinical stage, which defines secondary prevention.