Regarding the principles of screening for disease in a population, all of the following are TRUE EXCEPT:

## Screening Principles — What Makes a Disease Suitable for Screening **Key Point:** Screening programs are resource-intensive and ethically justified only when specific criteria are met. Not every disease is a candidate for population screening. ### Wilson & Jungner Criteria for Screening The WHO established ten criteria that a disease must satisfy to be suitable for screening: | Criterion | Rationale | |-----------|----------| | Important public health problem | High prevalence and/or significant morbidity/mortality | | Natural history well understood | Progression from latent → symptomatic stage must be predictable | | Recognizable latent/early stage | Disease must be detectable before symptoms | | Suitable screening test available | High sensitivity and specificity, acceptable to population | | Effective treatment available | Early detection must lead to better outcomes than late detection | | Agreed policy on who to treat | Clear management guidelines post-diagnosis | | Facilities for diagnosis/treatment | Infrastructure must exist to manage screen-positives | | Screening acceptable to population | Low cost, minimal harm, culturally appropriate | | Cost-effective | Benefits must justify expenditure | | Ongoing surveillance | Continuous monitoring of program effectiveness | **High-Yield:** The correct answer (option 4) violates the fundamental principle that screening should be **selective and targeted**. Screening all diseases indiscriminately wastes resources and causes harm (false positives, overdiagnosis, anxiety). ### Why Options 1, 2, and 3 Are Correct **Option 1 (Latent/early stage):** Essential — if a disease has no detectable pre-symptomatic phase, screening cannot work. Example: Colorectal cancer has a polyp → dysplasia → cancer progression. **Option 2 (High sensitivity):** Critical — a screening test must catch most true cases to be useful. Low sensitivity means missing cases, defeating the purpose of early detection. **Option 3 (Natural history understood):** Mandatory — we must know the disease's progression timeline, risk factors, and prognosis to design rational screening intervals and treatment thresholds. ### Why Option 4 Is Wrong **Clinical Pearl:** Screening is **not** a one-size-fits-all intervention. Screening for a rare disease with no effective treatment (e.g., untreatable genetic disorder) causes psychological harm without benefit. Similarly, screening for a disease with no latent phase (e.g., fulminant sepsis) is pointless. **Warning:** Overscreening and disease mongering are major harms in modern medicine. Screening programs must be evidence-based and justified by burden of disease and treatment efficacy. [cite:Park 26e Ch 10]