In this series of articles, our medical students will discuss a range of topics from medical ethics to the NHS to public health to medical conditions to clinical governance
Screening is a way of identifying disease in apparently healthy people; it is a form of secondary prevention. It is different from a diagnostic test as this is testing symptomatic, not asymptomatic, individuals of disease. The NHS, advised by the UK National Screening Committee (UK NSC), offers a range of screening programmes to different sections of the population who would benefit from it.
Screening offered by the NHS in England
Pregnancy; screening is offered for certain infections, genetic and physical congenital anomalies.
Neonates; Offered a newborn baby check, hearing check and blood spot test to screen for 9 rare conditions.
Diabetes checkup; From the age of 12, all people with diabetes are offered an annual eye check to check for signs of diabetic retinopathy.
Cervical cancer screening; Offered every 3 years for those aged 26 to 49, and every 5 years from the ages of 50 to 64.
Breast cancer screening; Offered to women aged 50 to 70. Women over 70 can self-refer.
Bowel cancer screening; Faecal Immunochemical Test (FIT) is offered to men and women aged 60 to 74. Endoscopic screening is offered to men and women in some parts of England.
Abdominal aortic aneurysm (AAA) screening; Offered to men in their 65th year. Men over 65 can self-refer.
What are the benefits of screening programmes?
Reduces the risk of disease progression and complications which may be harder to treat further down the line
Treatment is often more effective when used early
With the reduced the risk of disease progression and complications NHS resources are being saved further down the line
Reduces mortality rates through early detection of disease (NHS Breast Screening Programme may save around 1,400 lives per year)
Finding out that you have or are at an increased risk of a health problem helps people make better-informed decisions about their health
What are the limitations to screening programmes?
Finding out you may have a health problem can cause considerable anxiety.
Even if your screening test result is normal or negative, you could still go on to develop the condition
Screening tests are not 100% accurate (PSA screening dilemma)
The Prostate Specific Antigen (PSA) screening dilemma
Screening for prostate cancer is controversial. This is because although a recent European trial (ERSPC) showed a statistically significant reduction in the rate of death prostate cancer by 20% in men aged 55 to 69 years, it was associated with a high risk of over-diagnosis and over-treatment.
Up to 15% of men with prostate cancer have a normal prostate specific antigen (PSA) blood level. This means that there is a high false negative rate (low sensitivity) to this test. Also lots of men with an elevated PSA do not have prostate cancer, meaning that there is a high false positive rate (low specificity). Those men with false positives may undergo painful or potentially dangerous prostate biopsy. Furthermore, of those who do have prostate cancer, some have an aggressive form but other’s have a less aggressive form that would not have caused them any problems.
To help appraise the validity of a screening programme the Wilson and Junger Criteria is used (4);
The condition should be an important public health problem
There should be an acceptable treatment for patients with recognised disease
Facilities for diagnosis and treatment should be available
There should be a recognised latent or early symptomatic stage
The natural history of the condition, including its development from latent to declared disease should be adequately understood
There should be a suitable test or examination
The test or examination should be acceptable to the population
There should be agreed policy on whom to treat
The cost of case-finding (including diagnosis and subsequent treatment of patients) should be economically balanced in relation to the possible expenditure as a whole
Case-finding should be a continuous process and not a 'once and for all' project
Example of how the Wilson and Junger Criteria is used
Neonatal blood spot screening, performed at days 5-9 of life, tests for 9 rare conditions. Although the conditions are rare, this test is simple to perform with minimal discomfort to the neonate and brings enormous benefits. Early treatment for the identified condition can improve their health, and prevent severe disability or even death. For example neonates with congenital hypothyroidism can be given the hormone thyroxine and develop normally, when irreversible cognitive impairment would otherwise occur.