Paper-based diagnostic tests have been gaining a foothold in clinical applications, especially in the developing world, thanks to their low cost and ease of use. One issue with some of these tests is the requirement that a precise timer be used to gauge when to take the reading. Now researchers from Pennsylvania State University have developed a simple timer than can be built into paper diagnostics for a low cost, making implementation of these tests in difficult and poverty stricken environments easier and more straightforward:
The timer is made from a dye and the paraffin wax used in some candles. Addition of water, blood, urine or other body fluids starts the timer, and a color change signals when the time is up. The device has been modified to emit a buzz or other sound when the time is up, or even glow, the scientists note. When used with a test similar to the CHEMCARD glucose test, the timer was 97 percent accurate, slightly better than when a stopwatch was used.
American Chemical Society press release: Built-in timer for improving accuracy of cost saving paper-strip medical tests…
Abstract in Analytical Chemistry: Fluidic Timers for Time-Dependent, Point-of-Care Assays on Paper