Scientists have developed a test to find out which groups of people are more likely to develop bowel cancer.
Bowel cancer kills thousands of people each year
The Edinburgh researchers say they will be able to tell if a person is carrying faulty genes that can be linked to the cancer by using the screening method.
Faults in the genes MLH1, MSH2 and MSH6 are connected to some bowel cancers.
Scientists at Edinburgh University developed the test in a study involving 870 patients, the New England Journal of Medicine reports.
They took blood and tumour samples to look at their DNA.
Their findings showed that 38 (4%) of the patients had the faulty genes, higher than previous estimates.
Bowel cancer is common in the UK with 34,900 cases diagnosed every year.
It is hoped that the test will be able to detect people at risk before they develop the disease.
Professor Malcolm Dunlop, from the colon cancer genetics group of Edinburgh University, said: "This large study has allowed us to develop a new means to identify patient groups who are likely to carry genetic defects responsible for their bowel cancer.
"The model we developed is easily accessed on our website for clinicians who can then use the prediction to determine who needs genetic blood tests.
"Our method also shows that a higher proportion of bowel cancer patients fulfilled the criteria for having genetic faults than the current methods would suggest."
The study found that twice as many men carried the faulty genes as women.
The findings were welcomed by Professor Alex Markham, chief executive of Cancer Research UK.
He said: "These are very valuable findings that will help scientists better understand the process of bowel cancer development, particularly in people who are diagnosed at a young age."