The investigation of apparently healthy individuals to detect disease or risk factors for disease early in the natural history of the disease process.
Two important criteria for screening:
1) the particular disease that is detected by the screening would be expected to go on to cause significant morbidity and mortality
2) that treatment is available that is more effective in the early stages before symptoms occur than later when symptoms do develop – the treatment available must be able to alter the outcome if the disease is detected earlier.
Not possible to screen everyone identify those at higher risk
National Screening Committee (1998) criteria for appraising the viability, effectiveness and appropriateness of a screening program:
6.2.1 The condition should be an important health problem
6.2.2 The epidemiology and natural history of the condition, including development from latent disease, should be adequately understood and there should be a detectable risk factor, disease marker, latent period or early symptomatic stage.
6.2.3 All the cost effective primary prevention interventions should have been implemented as far as practicable
6.2.4 There should be a safe, simple, precise and validated screening test
6.2.5 The distribution of test values in the target population should be known and a suitable cut off level defined and agreed
6.2.6 There should be an agreed policy on the further diagnostic investigation of individuals with a positive test result an on the choices available to those individuals
6.2.8 There should be an effective treatment or intervention for patients identified through early detection, with evidence of early treatment leading to better outcomes than late treatment
6.2.9 There should be agreed evidence based policies covering which individuals should be offered treatment and the appropriate treatment to be offered
6.2.10 Clinical management of the condition and patient outcomes should be optimised by all health care providers prior to participation in a screening program
The screening programme
6.2.11 There should be evidence from high quality randomised controlled trials that the screening programme is effective in reducing mortality and morbidity
6.2.12 There should be evidence that the complete screening programme (test, diagnostic procedures, treatment/intervention) is clinically, socially and ethically acceptable to health professionals and the public
6.2.13 The benefit from the screening programme should outweigh the physical and psychological harm (caused by the test, diagnostic procedures and treatment)
6.2.14 The opportunity cost of the screening programme (including testing, diagnosis and treatment) should be economically balanced in relation to expenditure on medical care as a whole
6.2.15 There should be a plan for managing and monitoring the screening programme and an agreed set of quality assurance standards
6.2.16 Adequate staffing and facilities for testing, diagnosis, treatment and programme management should be available prior to the commencement of the screening programme
6.2.17 All other options for managing the condition should be considered (eg improving treatment, providing other services)”