Glycated Albumin Levels in Tears Allow Noninvasive Glucose Testing

The glucose test helps determine if a person’s glucose level is too high or too low, which can indicate the presence of Type 2 diabetes and other medical conditions. The two most common types of glucose testing are the fasting plasma glucose test and the random plasma glucose test.

Glycated albumin is albumin that has been glycated (bound to sugar). Albumin is the most common type of protein found in blood (~80% of circulating proteins) and is replaced in the body about every 20-25 days. Excessive glycation of albumin causes irreversible damage to organs and their vasculature.

Scientists at the University of Tokyo (Tokyo, Japan) recruited 100 adults (mean age, 50.87 years; 71% men) with diabetes from outpatient and inpatient practices. Participants had tear samples collected at the same time as a blood sampling tests. The team measured glycated albumin levels in tears with liquid chromatography-mass spectrometry, whereas blood sample levels were measured through an enzymatic method.

The investigators reported that glycated albumin levels were appropriately measured in 99 of 100 participants. Initial results showed a correlation between glycated albumin levels in blood and those measured in tears (beta = 0.722; 95% CI, 0.585-0.859). The correlation between tear levels and blood levels remained after adjustments for age, sex, nephropathy stage and obesity (beta = 0.738; 95% CI, 0.594-0.882). HbA1c was not assessed in the study.

Masakazu Aihara, MD, PhD, a project research associate and lead author of the study, said, “To achieve strict glucose control preventing diabetic complications, many patients take HbA1c tests in hospitals and some take self-monitoring of blood glucose. Continuous glucose monitoring has also been put into practical use, but all of these measurement methods are invasive, and it is a burden on the patients. We focus on tears, which can be collected with noninvasive ways, and found that the glycated albumin levels in tears and blood had strong correlation. Since glycated albumin reflects two week average blood glucose levels, it does not need to be measured as frequently as self-monitoring and can be used in the same way as HbA1c tests.”

Dr. Aihara added “The correlation of glycated albumin levels in tears and blood that we found in this study was much stronger than that of glucose levels, and a measurement method of tear glycated albumin can be used in clinical practice.” The study was presented at the European Association for the Study of Diabetes virtual meeting, held 21-25 September, 2020.

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