A simple blood test could warn people whether they are likely to suffer a heart attack within five years, scientists believe.
Researchers have discovered that high levels of antibodies produced by the immune system are linked to a low risk of heart problems, regardless of other risk factors.
The finding, which they described as "exciting", could mean that people currently on statins or beta-blockers no longer need them because their immune systems are strong enough alone to protect them.
Currently, doctors use factors such as age, sex, medical history, cholesterol levels and blood pressure to calculate the risk of heart disease.
The new test looks for levels of protective IgG antibodies that seem to shield the body from a heart attack even when cholesterol and blood pressure are high.
People with the highest number of antibodies had a 58 per cent lower risk of coronary heart disease or heart attack and a 38 per cent lower chance of suffering a stroke or other heart events during a five-year trial.
The team at Imperial College London and University College London studied more than 1700 people at risk of heart problems. Those with the lowest levels of antibodies had the highest risk of attack.
"Linking a stronger, more robust immune system to protection from heart attacks is a really exciting finding," said Dr Ramzi Khamis, lead researcher and consultant cardiologist at the National Heart and Lung Institute.
"As well as improving the way we tell who is at the highest risk of a heart attack so that we can give them appropriate treatments, we now have a new avenue to follow in future work.
"We hope that we can use this new finding to study the factors that lead some people to have an immune system that helps protect from heart attacks, while others don't.
"We also hope to explore ways of strengthening the immune system to aid in protecting from heart disease."
Measuring IgG, which is found in all bodily fluids, is simple and cheap. IgG antibodies protect against bacterial and viral infections.Researchers say the study focused on patients being treated for high blood pressure, and they now need to know whether the link also applies to other groups.