By Nick Triggle
Health reporter, BBC News
Health screening, on the face of it, seems like an excellent idea.
Strokes are one of the biggest causes of vascular disease deaths
Prime Minister Gordon Brown has pledged to make the NHS a preventative service as well as a curative service.
And disease screening is to be placed at the heart of the drive from later this year.
But screening is actually nothing new.
Breast and bowel cancer screening programmes are already being run across England - and they are due to be extended.
And the latest screening announcement, covering vascular disease such as heart problems and stroke, is in many respects already happening.
WHAT WOULD BE COVERED BY THE SCREENING
The programme is primarily aimed at people with vascular disease, which is mainly caused by a thickening of the arteries
The two biggest killers are heart disease and stroke, responsible for nearly 200,000 deaths a year - a much higher rate than other developed countries
Diabetes is one of the main risk factors for vascular disease an estimated 1m people are still not diagnosed in England
Diabetes is also linked to chronic kidney disease, which affects a tenth of the population, mainly the elderly
GPs already carry out checks for these diseases in patients they believe are at risk, by taking cholesterol, urine and blood tests.
But the prime minister wants to go further, introducing a national programme.
The move has angered doctors. At the end of last year, ministers told GPs they would be getting less money for treating such vascular conditions.
Instead, they would be expected to work longer hours to get their full bonus.
Dr Richard Vautrey, deputy chairman of the British Medical Association's GPs committee, said: "Last year they were talking about taking money from disease prevention, now they want to do this. We are very suspicious.
"Previous screening programmes have been introduced after much consideration and analysis of evidence. It doesn't seem like this is."
He says one of the risks of mass screening is that you end up medicalising vast swathes of the population.
"If you screen too many people you get a situation that everyone with any sort of abnormality is alerted. This can cause undue worry when the risk is very marginal."
Dr Tim Crayford, president of the Association of Directors of Public Health, agreed that this could be a risk.
"It is important that the way this screening is designed and funded is right. You don't want people to be diagnosed inaccurately.
"But generally speaking, this is a positive move. Preventative schemes have been under funded compared to some of the acute stuff.
"It is what public health is all about - identifying the problem before significant harm takes place."
Despite the announcements, there are many details that still need to be ironed out.
The government has said it wants GPs and private providers to carry out the screening alongside more diagnostic tests such as ultrasounds and blood tests.
It said the extra screening should start to be rolled out in 2008-9.
Ministers have named screening for abdominal aortic aneurysm, which can cause one of the body's main blood vessels to burst, as one of the priorities.
But doctors still say they are in the dark about who should be screened and how else it should be done.
Much of this detail is not expected to be announced until February, but some experts are already concerned about what will happen once a diagnosis has been made.
Peter Weissberg, medical director of the British Heart Foundation, said screening had the "potential to save lives".
But he added: "There is little point in identifying someone at risk without providing the resources to treat them.
"A national screening programme will cost a lot of money and cannot work unless it is underpinned with sound investment - and not at the expense of other health services."
And Dr Alan Maryon-Davies, president of the UK Faculty of Public Health, said this would mean extra dieticians, exercise co-ordinators, practice nurses and public health specialists would be needed.
"If you identify people with high cholesterol or glucose levels, you have then got to have the proper services to help them."