Tens of thousands of young people in Britain are to be screened for a genetic defect that can kill them in their twenties.

Under proposals to be announced next week by the National Institute for Health and Clinical Excellence (NICE), nationwide testing is to begin to detect those with genes that increase their blood cholesterol — and hence their risk of heart disease. The tests, which could cover children as young as 10, will be focused on those whose fathers or mothers are known to have high cholesterol levels.

It is thought that up to 120,000 people in Britain carry genes that cause high cholesterol levels. Carriers run the risk of developing heart disease at a much younger age than other people, and dying from it before they are aware of the risk.

The tests aim to detect familial hypercholesterolaemia (FH), the commonest genetic disorder among people of European descent.

So far, fewer than a fifth of the 120,000 carriers of the FH genes know that they have the condition. This represents “a systematic failure” of diagnosis by the NHS, according to Alan Rees, chairman of the charity Heart UK. “It’s a disgrace,” he said.

Many people with FH die suddenly of heart attacks that could have been prevented easily if they had been aware that they carried the mutant gene and had been treated with statins to lower their cholesterol levels.

The NICE guidance is expected to recommend “cascade screening”, in which the close relations of every identified FH sufferer are screened for the three genes that cause half of all cases.

The Netherlands has introduced such a scheme, with great success. NICE is understood to have concluded that cascade screening would be straightforward to introduce in Britain, would cost relatively little, and could save thousands of lives.

The average total cholesterol level for middle-aged men in Britain is about 5.5 mmol/litre, but people with FH may score as high as 15.

Their high cholesterol levels are caused by defects in the gene that transports cholesterol to the liver for disposal, and in other genes. A simple test, costing £200, can establish if someone is a carrier of any of these genes.

Children who carry the gene start to suffer from furred-up arteries as young as 8. By their twenties, the arteries may be as damaged as those of a 50-year-old, yet sufferers have no obvious symptoms and most are unaware of the risks that they run. The arrival of statins means that drugs can, if necessary, be taken for a lifetime, lowering the heart risk to normal levels.

“Statins will halve levels of the bad form of cholesterol,” said Dermot Neely, a consultant at the Royal Victoria Infirmary in Newcastle upon Tyne. “And they are as cheap as chips — cheaper, actually. The problem is getting people on to treatment before they have a heart attack. Heart attacks that occur at a young age are often fatal, so we need to identify FH as early as possible. We may need to start treating in childhood.”

In the US, children as young as 8 who suffer the condition are given statins. In Britain, Dr Rees said, there was no consensus over the age at which treatment should start, but clinical trials in patients from the age of 8 in the Netherlands had shown no ill-effects.

FH remains unrecognised by many GPs, he said. One of his patients, now 21, has been on statins since she was 14. She came off them to have a baby, which was born absolutely normally. When, after moving house, she went to her new GP for a fresh statin prescription, she was told that it was unthinkable to give statins to someone so young.

Dr Neely said that the new guidance would mean that there would in future be no excuses for GPs not treating these patients properly.

The key will be to identify cases. A parent has a 50-50 chance of passing on the gene to a child, so once an “index case” is identifed, close relations will be asked whether they want to be tested.

The new guidance will recommend that the children of those affected by FH should take the test by the age of 10. Those found to be positive will be advised about leading a healthy life, and counselled especially strongly not to start smoking. The first option for drug treatment is simvastatin, which is cheap, but for more severe cases more potent statins may be needed.

In extreme cases, a form of dialysis in which cholesterol is removed from the bloodstream may be considered.

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