Core Preventive Medicine: Epidemiology, Screening, and Prevention for the Occupational Physician
What the exam expects
Core preventive medicine tests whether you can reason from study design to causal inference to action. Know the measures cold: incidence vs. prevalence (prevalence = incidence × duration), attack rate for outbreaks, relative risk for cohort studies, odds ratio for case-control studies, and attributable risk as the exposure-attributable fraction of disease. Distinguish sensitivity (rules out disease when negative) from specificity (rules in disease when positive), and predictive values, which shift with prevalence-a common trap when applying a screening test to a low-prevalence workforce.
Prevention and screening logic
Be able to classify interventions: primary (remove exposure, immunize, engineer out the hazard), secondary (screening, biological monitoring), tertiary (rehabilitation, return-to-work). Screening criteria matter: the condition must be important, have a detectable latent stage, an acceptable test, and effective early treatment. Occupational examples include audiometry for noise, spirometry for respiratory hazards, and lead levels for biological monitoring.
Traps
Questions love to swap biological monitoring (internal dose) with biological effect monitoring (early change). Another trap: confusing confounding (a third variable associated with both exposure and outcome) with effect modification (risk differs across strata and should be reported, not adjusted away). Selection bias (healthy worker effect) systematically lowers observed occupational risk because healthier people stay employed.
Rule of thumb
If a question asks whether a screening program is justified, check the four boxes: important disease, detectable early stage, good test, effective early intervention. If any is missing, the answer is usually "do not screen."