Smartphone-Based Readerless System Measures Blood Glucose for Early Detection of Prediabetes

Prediabetes is characterized by high blood sugar levels that may progress to type 2 diabetes. Fortunately, this condition can be reversed with lifestyle changes such as a healthier diet and exercise, if detected early. However, many individuals with prediabetes are unaware of their condition, which puts them at greater risk of developing diabetes and complications such as heart disease, kidney failure, and vision loss. Screening for prediabetes typically involves laboratory testing at a healthcare facility or using a portable glucometer for at-home testing. Unfortunately, access and cost may limit widespread screening. Now, researchers have discovered an optimal approach to enhance early detection of prediabetes.

Researchers at the University of Washington (Seattle, WA, USA) have developed GlucoScreen, which takes advantage of the capacitive touch sensing abilities of smartphones to measure blood glucose levels without the need for a separate reader. This approach will help reduce the cost and increase accessibility of glucose testing, particularly for large-scale one-time screenings. GlucoScreen test strips measure the electrochemical reaction created by mixing blood and enzymes as an amplitude along a curve at a rate of five times per second. The strip then transmits this curve data to the phone encoded as a series of touches at variable speeds using pulse width modulation. “Pulse width” refers to the distance between peaks in the signal - in this case, the length between taps. Each pulse width represents a value on the curve, with a greater distance between taps indicating a higher amplitude of the electrochemical reaction on the strip.

The new GlucoScreen system has several advantages over traditional glucose testing methods. By leveraging the capacitive touch sensing capabilities of smartphones, it eliminates the need for a separate reader, making glucose testing more accessible and cost-effective for one-time screening of a large population. Additionally, the system does not require complicated electronic components, reducing the cost of manufacturing and power consumption compared to conventional communication methods like Bluetooth and Wi-Fi. The test strip is designed with photodiodes, which draw power from the phone's flash, eliminating the need for batteries or a USB connection. The GlucoScreen app walks users through the testing process, and after the data is transmitted from the strip to the phone, the app uses machine learning to analyze the data and calculate a blood glucose reading.

The researchers conducted both in vitro and clinical testing to evaluate their approach. In the clinical study, they enrolled 75 consenting patients who were scheduled to undergo a laboratory blood glucose test. The performance of GlucoScreen was compared against that of a conventional strip and glucometer, with the laboratory test serving as the ground truth. While additional testing is required, the preliminary results suggest that GlucoScreen's accuracy is comparable to that of a glucometer. Of significance, the system was found to be accurate at the critical threshold between a normal blood glucose level of 99 mg/dL or below and prediabetes, which is defined as a blood glucose level between 100 and 125 mg/dL. The researchers believe that GlucoScreen's performance will improve with further inputs.

“In conventional screening, a person applies a drop of blood to a test strip, where the blood reacts chemically with the enzymes on the strip. A glucometer is used to analyze that reaction and deliver a blood glucose reading,” explained lead author Anandghan Waghmare, a Ph.D. student in the Allen School’s UbiComp Lab. “We took the same test strip and added inexpensive circuitry that communicates data generated by that reaction to any smartphone through simulated tapping on the screen. GlucoScreen then processes the data and displays the result right on the phone, alerting the person if they are at risk so they know to follow up with their physician.”

“Because we use the built-in capacitive touch screen that’s present in every smartphone, our solution can be easily adapted for widespread use. Additionally, our approach does not require low-level access to the capacitive touch data, so you don’t have to access the operating system to make GlucoScreen work.” explained co-author Jason Hoffman, a Ph.D. student in the Allen School. “We’ve designed it to be ‘plug and play.’ You don’t need to root the phone — in fact, you don’t need to do anything with the phone, other than install the app. Whatever model you have, it will work off the shelf.”

“One of the barriers I see in my clinical practice is that many patients can’t afford to test themselves, as glucometers and their test strips are too expensive. And, it’s usually the people who most need their glucose tested who face the biggest barriers,” said Thompson, a family physician and professor in the UW Department of Family Medicine and Department of Global Health. “Given how many of my patients use smartphones now, a system like GlucoScreen could really transform our ability to screen and monitor people with prediabetes and even diabetes.”

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