Prevention is better than cure
The UK Government has recently decided to extend well-person screening of over 40s in the hope of increasing the detection of diseases at an early stage before the problem is too serious. The move is somewhat controversial because a substantial amount of health screening is already underway in UK general practice and there is some debate about the wisdom of putting more time and effort into potentially diminishing returns.
There are well-established criteria which should be satisfied before embarking on any health prevention programme aimed at specific population groups. In 1968 the World Health Organisation commissioned a report on health screening and Wilson and Jungner published their classic work entitled “Principles and practice of screening for disease”
“First do no harm” was set out by Hippocrates as a maxim for doctors and the Wilson-Jungner criteria are an attempt to keep enthusiasm on track and avoid the snags which can arise.
Their ten principles are:
1.The disease must be an important health problem
2.The natural history of the condition should already be well understood.
3.It must be recognisable at an early stage.
4.Treatment at an early stage should give an improved outcome.
5.A suitable test should exist which is reliable (producing few false positives or false negatives) and with a defined target population.
6.The test should be acceptable to patients.
7.Adequate facilities should exist to cope with the abnormalities detected.
8.There should be regular screening at repeated intervals when the onset is insidious
9.The chance of harm is less than the benefit.
10.Cost needs to be balanced against benefit (cost of case-finding includes diagnosis and treatment of patients diagnosed).
(modified from WHO Bulletin, Andermann et al 2008)
On the basis of these criteria, the UK National Screening Committee (UK NSC) has recommended screening for a number of conditions including breast cancer (women aged 50 and over, from age 47 by 2016) and cervical cancer (women aged 25 and over), bowel cancer screening for all men and women aged 60 and over. Pregnant women are offered tests to assess foetal problems. Young children are screened and school entry checks include height, weight, vision and hearing. All diabetics aged 12 and over are offered screening of the retina for diabetes-related changes which can lead to impaired vision. Both men and women, who are aged 25 and over and are sexually active, are offered annual chlamydia screening. GPs undertake regular well person checks including blood pressure and also urine testing for undiagnosed diabetes in older people as well as monitoring potential obesity and other lifestyle issues such as smoking and alcohol consumption. The list goes on!
One notable condition which is not included is prostate cancer screening. Screening has been shown to reduce mortality by 20% but is associated with a high level of over treatment because the untreated condition is generally slow growing anyway. The standard blood test (PSA, prostate specific antigen) is not fully reliable and generates a significant proportion with slightly raised levels who are then obliged to proceed to a prostate biopsy which is not attractive and overall the process leads to several weeks of anxiety whilst clarifying the false positive result. To save one life, 48 additional cases of prostate cancer need to be treated.
Prostate cancer screening at present is regarded as fulfilling only the first principle of screening convincingly and the UK NSC, in 1997, recommended that a prostate cancer screening programme should not be introduced in England. The policy was reviewed in December 2010 and no significant changes were made. It is due to be considered again in 2013/2014, or earlier if significant new evidence emerges. In the meantime, men will pay for the PSA test and the great majority get a normal result which is welcome .
Genetic testing is relatively cheap, quick and easy but the implications for national health services are huge. Genetic prediction of breast cancer is just one example amongst a growing number of possibilities and the recent brave move by Angelina Jolie to undergo anticipatory/preventive double mastectomy concentrates the mind if extrapolated over an entire national female population and funded out of public resources.
Prevention remains better than cure but only if we can rationalise our efforts and avoid massive information overload that could herald a false dawn.