Screening tests identify apparently healthy people who are at a higher risk of a condition. They ideally detect cancers at an early stage or where possible at a pre-cancer stage (e.g. the cervical screening program). A screening test should be acceptable, repeatable, sensitive and specific and simple to do and interpret. A normal or negative result would mean the person had a very low risk of having the condition at the time of testing and wouldn’t need further investigation, unless they became symptomatic. A positive result would warrant further diagnostic investigations. The screening programmes in Wales are managed by Public Health Wales.
The criteria (set out by the World Health Organisation) for a screening test are:
- The condition screened for should be an important one
- There should be a recognised latent or early symptomatic stage
- There should be a suitable test or examination which has few false positives (specificity) and few false negatives (sensitivity)
- The test or examination should be acceptable to the population
- The facilities for diagnosis and treatment should be available
- There should be an acceptable treatment for patients with the disease
- The cost, including diagnosis and subsequent treatment, should be economically balanced in relation to expenditure on medical care as a whole
The National Health Service in Wales offers the following screening programmes for cancer at the present time.
Bowel cancer – faecal blood test every 2 years between the ages of 60 and 74 for men and women
Breast – mammography every 3 years between the ages of 50 and 70 for women
Cervical – smear test every 3 years between the ages of 25 and 49 and then every 5 years between the ages of 50 and 64 for women
(exact details may vary in different areas of the United Kingdom)