• Will the benefits achieved and demonstrated in the research project be reproducible in a service setting, bearing in mind the fact that research is usually done by people who are keen on a particular topic and takes place under highly controlled circumstances?

• If more good than harm can be delivered in an ordinary service setting, can it be done at reasonable cost, taking into account not only financial costs but also opportunity costs?
In the United Kingdom a system has been set up to appraise research results and to make policy explicitly. The classic criteria produced by WHO in 1968 have been modified to take into account three issues related to 21st century decision-making:

• there is a focus on the quality of the research that produced the evidence and therefore the strength of evidence is taken into account when making decisions about screening;

• the classic criteria for screening give minimum attention to the harm that screening can do but in the consumer era the potential for harm has to be carefully considered;

• not only the financial costs but also the opportunity costs need to be estimated because shortage of skilled staff rather than shortage of money may be a key constraint.
In setting up a programme, it is important to plan and implement the programme as carefully as a new hospital, and it may take three or five years to introduce a programme. Once a programme gets into difficulty it may take many years and much money to rescue it.

When a programme is running, the UK National Screening Committee uses the principles of industrial quality assurance to:

• minimise the risk of errors;
• identify and deal with errors quickly;
• continually support the improvement of performance;
• set and re-set explicit standards of screening quality.

In the past screening has been developed principally as a public health service and individuals have been encouraged to attend for screening because high levels of coverage have been seen as important in achieving cost-effectiveness. However, the adverse reaction of both individuals, politicians and the press to problems in the delivery of screening have led to a more cautious approach being adopted. More emphasis is now given to informing people invited to screening about the risks and limitations of screening and considerable care is now taken to ensure that people who accept invitations for screening do so as a result of making an informed choice.