(CN) - Conventional blood sugar tests for diabetics don't account for individual differences and often lead to faulty results, so scientists have created a more accurate test that factors in the age of patients' blood cells to get a three-month average of blood sugar levels.
In a study published Wednesday in the journal Science Translational Medicine, researchers from Harvard Medical School and Massachusetts General Hospital say their model reduces the error rate of most commonly used test, known as A1C, by half. The new system can more accurately account for long-term blood sugar fluctuations in people with diabetes - more than 422 million individuals worldwide, according to the World Health Organization.
"What we currently deem the gold standard for estimating average blood glucose is nowhere as precise as it should be," said lead author John Higgins. "Our study not only pinpoints the root of the inaccuracy but also offers a way to get around it."
Higgins, an associate professor of systems biology at Harvard Medical School and a clinical pathologist at Massachusetts General Hospital, said that he and his team found that the A1C test led to off-target estimates in about a third of the more than 200 patients whose results were measured as part of their research.
According to the team, these inaccuracies stemmed solely from individual differences in the life span of a patient's red blood cells.
After analyzing the results, the team calculated age-adjusted estimates and tested their accuracy by comparing them to actual blood sugar levels measured directly by continuous glucose monitors — wearable devices that read a person's blood sugar every five minutes.
Combining the model with existing tests could lead to more accurate diagnoses, monitoring and nuanced treatments, the researchers said.
Estimating a person's three-month blood sugar average is important for disease control and the most accurate predictor of potential complications, according to the team. Consistently elevated blood sugar can damage the brain, heart, kidneys, eyes, nerves and other organs.
Since blood sugar can vary by the hour — or even by the minute — averages that account for fluctuations over an extended period are better indicators of disease status than measurements at a specific time.
Doctors often estimate blood sugar averages with the A1C test, which measures glycated hemoglobin — the amount of sugar soaked up by red blood cells over an extended period of time.
However, the test is inaccurate due to natural variations between people and can lead to drastically different medical conclusions. For instance, as little as 15 milligrams of glucose per deciliter of blood could signal the difference between low abnormal values in someone with diabetes and high normal values in a person without the disease. The A1C test can also produce identical readings that vary by as much as 60 milligrams per deciliter. While scientists are not sure what causes these discrepancies, the age of red blood cells is a leading suspect.
"Like a water-soaked sponge that's been sitting on the kitchen sink for days, older red blood cells tend to have absorbed more glucose, while newly produced red blood cells have less because they haven't been around as long," Higgins said.
The team said this dynamic can lead to two people with the same amount of sugar in their blood ending up with different results from their A1C test, depending on the average life span of their red blood cells.
To eliminate this variation, the researchers created a formula that accounts for the life span of a person's red blood cells that incorporates several values, such as directly measured glucose levels. The team then compared the age-adjusted blood sugar estimates to estimates measured by the standard A1C test, and then to readouts of glucose levels measured directly by continuous glucose monitors.
They found that the A1C test provided values that were off target by 15 milligrams per deciliter in more than a third of the patients - a significant disparity. By factoring in red blood cell age, Higgins' team reduced the error rate to 1 in 10.
Using the researchers' new approach, patients could wear a glucose monitor for a few weeks to establish the baseline of their blood sugar, which would also allow physicians to calculate the average age of a person's red blood cells before having the monitor removed.
"Physicians treating recently diagnosed patients would immediately know what a patient's red blood cell age is," Higgins said. "The patient's test results can then be adjusted to factor in the red blood cell age and get a result that more accurately reflects the actual levels of blood sugar, allowing them to tailor treatment accordingly."