Box 1.

Wilson and Jungner’s principles of screening

1. The condition should be an important health problem

2. There should be an accepted treatment for patients with recognized disease

3. Facilities for diagnosis and treatment should be available

4. There should be a recognizable latent or early symptomatic phase

5. There should be a suitable test or examination

6. The test should be acceptable to the population

7. The natural history of the condition, including development from latent to declared disease, should be adequately understood

8. There should be an agreed policy on whom to treat as patients

9. The cost of case-finding (including a diagnosis and treatment of patients diagnosed) should be economically balanced in relation to possible expenditure on medical care as a whole

10. Case-finding should be a continuous process and not a “once and for all” project