Health Promotion and Disease Prevention
Levels of Prevention
Candidates must distinguish primary (prevent disease before it occurs), secondary (early detection), and tertiary (limit disability and complications) prevention. Know the principles of screening: the condition must be important, have a detectable preclinical phase, an acceptable test, and effective early treatment. Understand lead-time bias, length-time bias, and overdiagnosis, which make survival look better without changing mortality. Know vaccination principles, including herd immunity and contraindications to live vaccines in immunocompromised patients and pregnancy.
Counseling and Risk
Understand behavioral counseling for tobacco, alcohol, diet, activity, and sexual health, and the value of brief motivational interviewing. Know the difference between absolute and relative risk reduction when counseling patients about preventive therapy. Recognize the role of social determinants in prevention and the importance of tailoring recommendations to risk.
Traps
Frequent traps: recommending a screening test outside the evidence-based age or risk group, confusing a risk factor with a screening test, and interpreting improved survival as proof that screening saves lives when lead-time bias explains it. Another trap is recommending a live vaccine to a patient on immunosuppression.
Worked Example
Rule of thumb: before recommending screening, ask whether early detection changes outcomes in this population. A test that finds more disease but does not reduce mortality may simply increase overdiagnosis and harm. Counsel with absolute numbers: a 20% relative reduction can be a small absolute benefit if baseline risk is low.