## Wilson and Jungner Screening Criteria **Key Point:** Wilson and Jungner (1968) established 10 criteria for evaluating screening programs. No screening test achieves 100% sensitivity and specificity — this is an unrealistic and unnecessary prerequisite. ### The 10 Criteria (Essential Ones) | Criterion | Rationale | |-----------|----------| | Disease is important health problem | Justifies resource allocation | | Natural history well understood | Identifies latent/early stage | | Recognizable latent/early symptomatic stage | Screening must detect disease before symptoms | | Suitable test available | Acceptable, valid, reliable | | Test acceptable to population | High uptake required | | Early treatment more effective than late | Justifies intervention | | Facilities for diagnosis/treatment available | Infrastructure must exist | | Agreed policy on management | Clear referral pathways | | Cost-effective | Economically justified | | Screening should be continuous | Not one-time event | **High-Yield:** The phrase "100% sensitivity and specificity" is a **trap answer**. Real-world screening tests operate with trade-offs: - High sensitivity = more false positives (acceptable for serious diseases like cancer) - High specificity = more false negatives (acceptable for less serious conditions) **Clinical Pearl:** A screening test with 95% sensitivity and 90% specificity is considered excellent in practice. The goal is to optimize the **positive predictive value (PPV)** and **negative predictive value (NPV)** for the target population, not achieve perfection. **Mnemonic:** **SNOUT & SPIN** - **SNout**: High **Sensitivity** rules **OUT** disease (negative test excludes diagnosis) - **SPIn**: High **Specificity** rules **IN** disease (positive test confirms diagnosis) Screening prioritizes sensitivity (catch all cases early), while diagnostic tests prioritize specificity (confirm the diagnosis).
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