Engineers at California Institute of Technology in Pasadena and the medical device company LeukoDx in Jerusalem, Israel developed a portable device to count white blood cells requiring only a drop of blood and a few minutes to run. The team led by Cal Tech electrical engineering professor Yu-Chong Tai published its findings in the 7 April issue of the journal Lab on a Chip (free registration required).
Measuring a person’s white blood cell count gives an indication of the body’s response to infection or disease. Current equipment for counting white blood cells, also known as leukocytes, are large devices that need a full vial of blood to run and several days to process the results.
Tai and colleagues Wendian Shi, Luke Guo, and Harvey Kasdan — chief technologist at LeukoDx — devised a test using three different dyes to stain white blood cells with a flourescent agent so they emit a glow under a laser light. One dye bonds to DNA in the nucleus of the white blood cells, so they can be distinguished from red blood cells, while the the other two dyes help distinguish between the various subtypes of white blood cells.
The test system uses a microchannel, about 50 micrometers long, made of silicone that restricts its flow of blood in the stained sample to one white blood cell at a time. The cells flow one at a time under a laser light that causes the cells to light up with either a red or green color. The test system then detects the intensity of the red and green glow to determine and count the type of white blood cells.
The prototype device developed by the Cal Tech and LeukoDx team measures 30 x 23 x 13 centimeters (12 x 9 x 5 inches) and can fit into a small suitcase. The device contains a cartridge with the new testing technique that distinguishes among the four major types of white blood cells — lymphocytes, monocytes, eosinophils, and neutrophils — as well as basophils that comprise less than 1 percent of white blood cells and are not usually measured in conventional counts.
The researchers report measurements from the prototype white blood test counter were similar to those taken from conventional equipment. “The white blood cell counts from our new system closely match the results from tests conducted in hospitals and other central clinical settings,” says Tai. “This could make point-of-care testing possible for the first time.”
LeukoDx is developing a commercial version of the system for point-of-care testing, a market that the company says is expected to reach $16.5 billion by 2016.
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