Rather than going through the cumbersome and sometimes painful routine of drawing blood, diabetes patients may be able to use their tears, researchers from the University of Michigan reported in Analytical Chemistry. In animal studies, the scientists found that glucose levels from the tears of rabbits could accurately measure blood glucose (sugar) levels using an electrochemical sensor device.
Lead researchers, Mark Meyerhoff and team explained that approximately 5% people globally have diabetes. With rising levels of obesity worldwide, the number of patients with diabetes type 2 is set to rise considerably.
The researchers set out to determine whether they could develop a new, pain-free device that could detect tear-glucose levels, rather than having to draw blood.
Patients with diabetes may have to draw blood from about two to ten times daily to test their blood glucose levels. A considerable number of diabetics do not draw blood as often as they should, because of the discomfort and pain it causes. This may lead to poor glycemic control. Long-term poor glycemic control increases several risks and complications linked to the condition, especially microvascular complications which can lead to neuropathy and the development of foot ulcers, retinopathy and other diseases and conditions.
Drawing blood several times a day can be painful and raises the risk of infection
The investigators say that according to their findings, tears can provide as accurate a reading as picking the finger and testing blood directly.
The authors wrote:
". . . . it may be possible to measure tear glucose levels multiple times per day to monitor blood glucose changes without the potential pain from the repeated invasive blood drawing method."
Their sensor has is extremely sensitive and can achieve extremely low detection limits of 1.5 ± 0.4 μM of glucose (S/N = 3). This is enough to measure tear-fluid glucose levels, with a glucose sensitivity of 0.032 ± 0.02 nA/μM. The sensor's capillary tube only requires 4-5 μL of tear fluid when the needle sensor is inserted into the capillary.
In an Abstract in the journal, the researchers wrote:
"A strong correlation between tear and blood glucose levels was found, suggesting that measurement of tear glucose is a potential noninvasive substitute for blood glucose measurements, and the new sensor configuration could aid in conducting further research in this direction."
Written by Christian Nordqvist