Doctors need to do more to get at an important indicator of a patient’s heart disease risk by asking about his or her family tree, a new study suggests.

Researchers, writing in the Annals of Internal Medicine, found that nearly one in five patients with significant heart-disease risks may escape their doctors’ attention, simply because the physician doesn’t ask about hereditary risks.

The American Heart Association issued guidelines for heart-risk screening in 2010, urging doctors to ask about family histories of heart disease.

But the new study, funded by the United Kingdom Department of Health, found many physicians aren’t following the guidelines. The research involved 748 patients -- aged 30 to 65 – and found up to 18 percent of patients were at high risk of heart disease, but were never asked about family history.

“Approximately 20 percent of patients in an unselected internal medicine practice were at an increased risk that was not documented in reviewed chart notes,” researchers concluded. “Targeted family history analysis reveals patients who require increased medical surveillance, preventive measures, or genetic counseling/testing.”

Nadeem Qureshi, the lead researcher and a professor at the University of Nottingham's Faculty of Medicine and Health Sciences, said taking a family history is a low-cost way to identify patients at risk.