A new study, conducted by Mark Meyerhoff and Phillip J. Elving, Professor of Chemistry, along with their colleagues from the University of Michigan, has suggested that it may be possible for scientists to develop a device that measures blood sugar levels through tears instead of blood. Laboratory tests of rabbits, used as surrogates for humans in such experiments, showed that levels of glucose in tears track the amounts of glucose in the blood.
On the run up to World Diabetes Day on November 14, the new findings could usher in a diagnostic change, in the manner in which blood sugar levels are currently tested. The study, published in the journal Analytical Chemistry, noted that researchers at the university have developed a device that detects dilute levels of sugar, or glucose, in tears.
If the Michigan study reaches ground reality, it could be a tearful adieu to the prick for diabetes checks. Although current blood test monitors make blood sugar tests less painful, these are definitely not as painless as the shedding of a single tear.
According to the World Health Organization (WHO), diabetes causes a staggering US$378 billion in global health care spending. The WHO predicts an increase to US$490 billion by 2030, saying that diabetes results in high health care costs, the loss of labor productivity and reduced economic growth.
If WHO estimates are to be believed, more than 346 million people worldwide have diabetes and this number is likely to more than double by 2030 without intervention.
In addition, data released by WHO states that preventable deaths from diabetes, heart diseases and strokes are causing China, Russia and India to lose US$558 billion, US$303 billion and US$237 billion, respectively, in foregone national income.
In such a scenario, scientists have reported developing successful electrochemical devices with the potential to measure blood sugar levels from from tears. This is expected to save the world's 350-odd million diabetes patients the discomfort of pricking their fingers for droplets of blood used in traditional blood sugar tests.
It is essential for diabetics to monitor their blood glucose levels several times a day to make sure they are within a safe range. Current hand-held glucose meters require a drop of blood, for which patients are required to prick their fingers with a small pin or lancet. This step, for some patients, is discouraging as it can be painful enough, particularly if it is to be done several times a day.
... 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, said the researchers.
Meyerhoff and his colleagues explained that about five percent of the world's population and about 26 million people in the U.S. have diabetes. The disease is a fast-growing public health problem because of a sharp global increase in obesity, which makes people susceptible to developing Type 2 Diabetes.
A similar alternative was attempted by Jeffrey LaBelle, a biomedical engineer at Arizona State University. In collaboration with researchers from the Mayo Clinic, LaBelle's attempted to create a sensor which when placed in contact with the white of the eye for five seconds, could then be pressed into a device for a reading.
Scientists have pointed out that although medical investigations using tears appeared as early as 1937, the logistics in working with tears as a diagnostic point of departure had its engineering pitfalls. The Michigan researchers point out a similar problem. Apparently, the levels of glucose in tears have been found to be typically 30-50 times lower than in blood, and that presents a challenge - to engineer a sensor sensitive enough to work with small amounts of fluids.
However, experts believe that tears may never completely replace blood tests. Although tear glucose correlated to blood glucose in each animal in the University of Michigan study, there were different correlations between individual rabbits. They explained that although the University of Michigan team seemed to show a good correlation between the tear glucose and blood glucose, they would have to repeat the results with other animals, healthy individuals and in diabetics.
The use of tears as an alternate sample to assess blood glucose in human subjects will likely require that the ratio of glucose in tears and blood be established first for a given individual, the study authors wrote. So, if the technology is one day used in people, each person would have to calibrate their tear sensors to their blood glucose level.
Researchers also explained that the major challenges for tear drop evaluations were evaporation, the lower concentration of glucose in tears and that of volume - meaning that it is easier to procure a few more drops of blood than it is tears.
Currently, the Food and Drug Administration (FDA) has approved glucose meters that do not require patients to prick their fingers but can be used only to get additional readings between regular testing.