UK Screening Programmes

The classic criteria, originally set out by Wilson and Jungner and developed since by the UK National Screening Committee (NSC), can be summarised under three headings, although this is a simplified summary rather than the complete set of criteria. The condition must be an important health problem with a understood natural history and a recognisable early or latent stage, since there is no point detecting something earlier if nothing meaningful happens in between. The test must be simple, safe, acceptable to the population, sufficiently accurate, and have an agreed cut-off, recognising that any cut-off trades false positives against false negatives. The programme must have an effective intervention available for those identified, robust evidence that the complete screening pathway improves important health outcomes with benefits outweighing harms and costs, acceptable cost-effectiveness, and quality assurance with equitable access. Randomised evidence of mortality reduction is highly valuable but is not the only evidence used in every programme decision.

Two biases explain why screening can appear effective when it is not, and both are examinable. Lead-time bias is the apparent lengthening of survival that occurs simply because diagnosis happened earlier, without the date of death changing at all. Length-time bias is the tendency for screening to preferentially detect slowly progressive disease, because fast-growing disease appears and presents between screening rounds, so the screen-detected group looks to have a better prognosis than it truly does. Overdiagnosis is a related but distinct problem: the detection of disease that would never have caused symptoms or death in that person's lifetime, which converts a healthy person into a patient and exposes them to treatment they did not need. It is closely linked to length-time bias but is not simply an extreme form of it, since overdiagnosis concerns disease that would never progress rather than disease that progresses slowly. Together these are the reasons a programme is judged on whether the pathway improves health outcomes rather than on survival among those screened.

The UK National Screening Committee advises ministers and the health services across all four nations, but each nation makes and implements its own screening policy, so programmes and eligible ages can differ between them. Recommendations are evidence-based and periodically reviewed, so the list changes. Broadly the programmes divide into three groups. Antenatal screening includes screening for infectious diseases in pregnancy, sickle cell and thalassaemia, and fetal anomaly. Newborn and infant screening includes the newborn blood spot test, newborn hearing screening, and the newborn and infant physical examination which checks eyes, heart, hips and, in boys, testes. Adult screening includes cervical screening, breast screening, bowel cancer screening, diabetic eye screening for people with diabetes, and abdominal aortic aneurysm screening offered to men in their sixty-fifth year. A lung cancer screening programme has been introduced, targeting people at higher risk on the basis of smoking history, having previously run as a targeted lung health check.

Prostate cancer is the most instructive current example and the position has recently changed. Population screening for prostate cancer is still not recommended, because the prostate specific antigen test performs poorly enough that the harms of overdiagnosis and unnecessary treatment outweigh the benefits at population level. However, targeted biennial testing is now recommended for men aged forty-five to sixty-one who have a pathogenic BRCA2 variant together with a family history of breast, ovarian, pancreatic or prostate cancer. Targeted screening was not recommended for other risk groups, including men with a family history alone. Implementation differs between the four nations. There is no national screening programme for most other cancers, for osteoporosis or for cardiovascular disease as such, although the NHS Health Check in England offers structured cardiovascular risk assessment to adults in a defined age range, which is risk assessment rather than screening for a single condition. Cardiac screening in athletes sits outside the national programmes entirely: it is undertaken by sporting bodies rather than the health service, the condition prevalence is very low, false positives are common and consequential for a career, and it is covered separately in the sports cardiology material. The principles for judging it, however, are exactly those set out above.

• •Screening proactively offers a test to an asymptomatic population or defined risk group, not always to entirely healthy people, and every programme causes some harm so must be judged on net benefit.
• •Criteria can be summarised under the condition, the test and the programme, though this is a simplified summary; a good test alone is not sufficient justification.
• •Lead-time bias lengthens apparent survival purely because diagnosis occurred earlier, with no change in date of death.
• •Length-time bias means screening preferentially detects slowly progressive disease; overdiagnosis is related but distinct, detecting disease that would never have caused harm at all.
• •Programmes divide into antenatal, newborn and infant, and adult; adult programmes include cervical, breast, bowel, diabetic eye and abdominal aortic aneurysm screening, with lung cancer screening for those at higher risk. The committee advises all four nations but each sets its own policy.
• •Population prostate screening is not recommended, but targeted biennial testing is now recommended for men aged forty-five to sixty-one with a pathogenic BRCA2 variant and relevant family history. Implementation differs between the four nations.