A "life-saving" programme of tests for an inherited high cholesterol condition has been launched across the UK with £1 million of funding from the British Heart Foundation.
The aim is to identify the one in 200 families whose members carry the gene for familial hypercholesterolaemia (FH), which can cut decades off a person's life.
Undiagnosed FH leaves individuals at high risk of developing heart disease and dying suddenly at a young age from a heart attack.
On average, the untreated condition shortens life expectancy by 20 to 30 years. But if spotted early, treatment with cholesterol-lowering statin drugs, lifestyle advice and careful monitoring can allow people with FH to live as long as anyone else.
FH is caused by a faulty gene that raises levels of the harmful form of cholesterol, low-density lipoprotein (LDL) from birth. At least 85% of those affected by the condition are undiagnosed.
The new scheme involves specialist nurses carrying out simple DNA blood tests to see if individuals with symptoms of high cholesterol carry the FH gene.
If the gene is discovered, other family members are then referred for "cascade" testing.
Steve Humphries, British Heart Foundation (BHF) professor of cardiovascular genetics at University College London, said: "With an estimated one in 200 hundred families carrying an FH-causing faulty gene in the UK, the introduction of cascade testing represents a huge opportunity to identify and treat people before they suffer from potentially life-threatening heart problems.
"After so many years of carrying out the laboratory research on FH, I am delighted now to see genetic testing being rolled out nationwide. But with such a high number of people remaining undiagnosed there is still more to be done if we're to get a complete picture of how FH affects the UK population."
The £1 million funding from BHF will pay for a dedicated team of specialist FH nurses.
An earlier pilot scheme in Wales jointly funded by BHF and the Government identified 1,183 people likely to have FH.
The tests showed that 492 of these individuals carried the faulty gene. Their cholesterol levels were subsequently brought down to the normal range by statin treatment.
Before the introduction of the FH nurses, only 97 of the Welsh group were known to have FH. The pilot was so successful that a decision was taken to extend it across England and Scotland.
Parents with the FH gene have a 50/50 chance of passing it on to one of their children.
More than half of men with the gene will develop heart disease and possibly die from a heart attack before the age of 50.
Among affected women, more than 30% are at risk of having a fatal heart attack by their 60th birthday.
Dr Tim Chico, consultant cardiologist at the University of Sheffield, said: " This life-saving programme has many important implications. It is supported by the hard work of hundreds of BHF volunteers and fundraisers, who deserve great credit for their efforts. It underlines the important role of the BHF in funding both research and clinical services.
"A new era in medicine is beginning; it will become increasingly common that genetic findings in relatives impact on the health and treatment of other individuals. This will allow us to tailor the right preventative drugs to those patients who have most to gain from treatment.
"Given recent adverse publicity, this is a useful reminder that for patients with FH, or those who are otherwise at high risk of heart disease, statins unquestionably save lives."
The National Institute for Health and Care Excellence (Nice) has estimated that if half the predicted relatives of people with FH are diagnosed and treated, it could save the NHS £1.7 million a year.