A screening programme is to be rolled out across England to identify whether tens of thousands of relatives of people with a defect that causes heart attacks are also at risk.
Health watchdog the National Institute for Health and Clinical Excellence (NICE) hopes that the tests will identify up to 100,000 people with familial hypercholesterolaemia (FH), a genetic defect that causes high cholesterol.
People with FH are at higher risk of heart attacks as the condition causes the narrowing of the arteries to speed up. Without treatment, half of men with FH will have a heart attack by the age of 50 and a third of women will have one by the time they are 60.
Although some 15,000 people in the UK are known to have FH, health experts think a further 95,000 or so remain undiagnosed.
NICE is recommending "cascade testing" of people deemed most at risk, namely "first-degree" relatives - parents, siblings and children - of those known to have FH. It also recommends that children are tested before the age of 10, but not before they have reached two years of age.
The screening will test DNA and cholesterol levels, and anyone diagnosed with FH will be offered cholesterol-busting statins to cut the chances of a heart attack.