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New Blood Sugar Test for Diabetes Cuts Diagnostic Errors in Half

Current tests of blood sugar levels may be skewed by the age of the red blood cells measured, according to the new study. | iStock Photo

A new test can cut errors in measuring blood sugar levels by 50%, compared to the current widely-used blood test, according to a study of more than 200 diabetic patients.

The findings open the door to personalized diabetes monitoring for more than 400 million people worldwide who rely on blood testing to keep their risk of diabetes-related complications in check.

"Patients and their doctors use this blood sugar result to guide future treatment choices, doses, and schedules," said John Higgins from Harvard Medical School and Massachusetts General Hospital. "The new method can help personalize diabetic monitoring by adjusting for the patient's own blood cell age to provide a more accurate blood sugar measurement."

The study appears in the 5 October issue of Science Translational Medicine.

Diabetic patients suffer from high blood glucose or sugar, putting them at risk of heart disease, stroke, kidney failure, nerve damage, blindness, and other complications. Closely monitoring blood sugar levels allows patients to adjust their medications or diet as needed.

The standard blood test, called the A1C test, measures the amount of glucose that sticks to hemoglobin, the oxygen carrier inside red blood cells. Because many factors can influence this process, however, A1C test results can vary substantially. For example, patients with identical A1C test readouts can have very different true sugar levels.

"Currently available tests are often inaccurate, providing significant under-estimates or over-estimates of blood sugar," said Higgins. "Under-estimates give patients a false confidence that they are doing what they can to limit their risk of these complications, depriving them of the opportunity to do more. Over-estimates provide a falsely critical assessment of patient efforts and may increase their risk for hypoglycemic [low blood sugar] episodes, which can be dangerous in the short-term."

To develop a more accurate method, Higgins and colleagues designed a mathematical model of glucose chemistry and red blood cell turnover and combined it with large data sets of patient glucose measurements.

The researchers pinpointed the age of blood cells in different patients as the major source of A1C variation. Because older red blood cells have had more time to pick up sugar in the blood, they can potentially skew the A1C test result, which averages glucose across red blood cells of all ages in the bloodstream.

To determine the age of the blood cells, Higgins and his colleagues developed an equation that compares glucose levels obtained by the A1C test with another method called continuous glucose monitoring.

"We expected that blood cell age was an important factor … but we were surprised to find that it can explain all of the inaccuracy of the current test," said Higgins.

By taking the age of patients' blood cells into account, the researchers' model, when tested in more than 200 diabetic patients, reduced the error rate from one in three patients with the standard blood test to an error rate of one in 10.

"While we expected that blood age was stable enough that we could estimate it and use the estimate to provide some increase in accuracy, we did not think we would reduce errors by more than 50% as we did," said Higgins.

With further development, the approach could help guide more precise monitoring and treatment for diabetic patients. Patients at home, whether using the standard A1C test or a continuous glucose monitoring device, can use the new method to perform a calculation that would provide more accurate real-time estimates of their recent blood sugar, according to Higgins.

"It would be easiest for patients if the device and assay manufacturers integrated the calculation with their measurement systems," said Higgins.

The new method of estimating blood sugar could also help researchers evaluate new therapies for diabetes in clinical trials, he noted.