Doctors can accurately determine which people with mild high blood pressure face serious risk of heart attacks by measuring a key blood protein, researchers said.

The researchers recommended that measuring the substance should become part of routine care for everyone with high blood pressure because those at risk could be truly targeted for treatment.The researchers found that those with high levels of renin are five times more likely than people with low levels to suffer heart attacks.

If their work is confirmed by others, the discovery could provide physicians with a way of tailoring treatment for people with mild to moderate high blood pressure, concentrating most on those whose high renin levels put them at elevated risk of heart attacks.

"It will help us to identify a group of patients who can be spared the hazards of drug treatment. And in those who need treatment, it will help us choose the proper drug," said Dr. Michael H. Alderman of Albert Einstein College of Medicine in New York, who directed the study.

The implications of the research are controversial, however, and some specialists said they were unsure what, if any, impact it will have on day-to-day care of people with hypertension.

An estimated 62 million Americans have elevated blood pressure. While the disease leads to strokes, heart failure and kidney disease, its biggest hazard is its contribution to heart attacks.

Because there is no way to determine who will be harmed by mildly elevated blood pressure, doctors routinely give pressure-lowering drugs to all patients who cannot bring down their blood pressures by losing weight or changing their diets.

Alderman said that if such people have low renin levels, however, drug treatment may be unnecessary, because their heart attack risk is already low.

Dr. Victor J. Dzau of Stanford University School of Medicine called the results "intriguing and important," but questioned Alderman's assertion that they may allow people to escape treatment for high blood pressure.