A test that detects blood sugar levels over a period of several weeks not only is the best way to diagnose diabetes but could identify with greater precision than the standard approach who is at risk of contracting it, investigators said.

In a study involving over 11,000 people with no history of diabetes, hemoglobin A1c test more accurately determined who would develop the disease compared with glucose testing, which measures blood sugar levels at a point in the time.

The A1c test was also able to better predict the risk of stroke (CVA), heart disease and death from diabetes, the researchers report in the New England Journal of Medicine.

The team found that people who had A1c levels of 6 percent or more were at greater risk of developing diabetes.

“The A1c has significant advantages over blood glucose test,” said Dr. Elizabeth Selvin from Johns Hopkins University in Baltimore and leader of the study.

The blood sugar levels can vary from day to day and from hour to hour.

The A1c test is more reliable, repeatable and allows doctors to follow the average glucose levels over time. The quantities are not affected by stress and disease and patients do not have to fast before the test, as with glucose, the researchers said.

In January, the American Diabetes Association recommended A1C test to control the disease and to identify people who may be at risk of developing it.

In the study, Selvin’s team examined blood samples from 11,092 middle-aged adults without diabetes whites and blacks, drawn between 1990 and 1992.

The researchers compared the A1c test with fasting glucose to identify those most at risk for diabetes, heart disease and stroke and die.

During the 15 years of follow up, 2251 people were diagnosed with diabetes, 1198 were heart disease, 358 stroke and died 1447, the team said.

Doctors think that it is normal to have A1C levels between 5 and 5.5 percent. With each increase, the researchers found that increased the incidence of diabetes.

Persons with levels between 6 and 6.5 percent were nine times more likely than those within the normal range to develop the disease.

According to the study, currently there are 9 million Americans with undiagnosed diabetes.

Diabetes occurs when the body becomes unable to use insulin effectively. The blood sugar levels rise, leading to complications such as heart disease, blindness and kidney failure.

About 24 million Americans have diabetes, according to the Centers for Disease Control and Prevention (CDC for its acronym in English).

The disease costs the United States about 132,000 million dollars a year on disability, lost productivity and premature deaths.