Questions: Levels of Disease Prevention

Question 1

A community health program offers free colonoscopies to asymptomatic adults over age 50 to detect colorectal polyps before they progress to cancer. This intervention is an example of:

• A. Primary prevention
• B. Secondary prevention
• C. Tertiary prevention
• D. Primordial prevention

Answer: (B)

Secondary prevention targets asymptomatic individuals to detect disease (or pre-disease) early, before symptoms appear, in order to interrupt progression. Colonoscopy screening in asymptomatic adults fits this definition precisely. Primary prevention would be reducing risk factors before any pathological change (e.g., promoting a high-fiber diet). Tertiary prevention would be managing colorectal cancer once diagnosed to limit disability. Primordial prevention addresses the social conditions that give rise to risk factors in the first place.

Question 2

Tertiary prevention is not truly 'prevention' because it occurs after disease has already developed.

• T. True
• F. False

Answer: False

Tertiary prevention is a genuine and important form of prevention — it prevents further deterioration, disability, and complications in people with established disease. Cardiac rehabilitation after a myocardial infarction prevents a second cardiac event; tight glycemic control in a diabetic patient prevents neuropathy and nephropathy. The word 'prevention' refers to preventing downstream consequences, not the original disease. Conflating 'prevention' with 'stopping disease from occurring at all' is a common error that undervalues this tier of care.

Question 3

Why is the claim 'more screening is always better' a misconception in secondary prevention?

Model answer: Screening imposes real costs even when tests are free: false positives trigger unnecessary follow-up procedures with their own risks and harms; overdiagnosis detects conditions (e.g., slow-growing prostate cancers) that would never have caused symptoms, leading to overtreatment; and screening resources spent on low-risk populations may not be cost-effective compared to higher-priority interventions. Screening is beneficial only when the target disease has sufficient prevalence, the test is sensitive and specific enough, effective treatment exists, and benefits outweigh harms in the screened population.

This misconception is common because 'catching things early' sounds intuitively good. The key insight is that screening is a population-level intervention that must be evaluated on net benefit across the entire screened population — including the harms to people who test false-positive or are overdiagnosed.