Successful screening initiatives depend on 'blindingly simple' mechanisms for picking up often highly complex conditions, says the director of the UK's screening review body.
National Screening Committee director Dr Anne Mackie told GP that it was no easy task to condense the subtleties of clinical evidence and patients' individual risk into national guidelines.
'Life is very complicated but screening programmes need to be blindingly simple,' Dr Mackie said.
National screening programmes must be hugely prescriptive to provide a consistent service, she said. 'One of the consequences is that we put together the information to help people decide if they actually want to be screened.'
The committee is developing practical tools for GPs, to help them explain the implications of screening results - both private and NHS - to patients.
'We are looking to develop resources for GPs so that, for example, if a woman comes in to see a GP and says she and her partner are both sickle cell carriers, the GP can tell her the risks of having a child with the disease,' she said.
'Or if patients say they have had their genome scanned for genes associated with an increased risk of developing diabetes, GPs will be able to give advice and tell them how they can reduce their risk.'
The committee is also developing advice for GPs on the implications of private screening, after suggestions that private firms are approaching GPs to promote their services.
But providing unbiased information on the potential risks and benefits of screening poses challenges, Dr Mackie said.
'We need to be careful that we balance the positives with the negatives and do not persuade people to have tests,' she said. 'People need to choose.'
At present, the committee is reviewing its policies on prostate screening and tests for newborn babies.
Potential additions to national screening plans are weighed up on the basis that they should do more good than harm at reasonable cost, Dr Mackie said.
'We use a broad view of costs, not just those that fall on the NHS,' she added. 'We take into account costs to the individual and society, and psychological costs, which for screening can be significant.'
The evidence for prostate screening is being examined by academics, with a decision expected in the spring, she said.
The committee aims to decide by autumn whether to change its advice not to use PSA to screen for prostate cancer.
'Trials suggest that you need to treat about 48 people to cure one,' Dr Mackie added. 'We need to nail it down a bit harder.'
The committee is also looking at whether to extend the tests undertaken on the bloodspot taken from newborn babies, Dr Mackie added.
'We need good evidence as to whether introducing these tests is the right thing, particularly with rare conditions, because of the risks of generating false positive results, leading to unnecessary anxiety for parents.'