The science behind the device is an innovative detection assay of dyes that stain leukocytes so they will fluoresce and enable differentiation of white blood cell subtypes
Over the last couple of years, medical laboratory technology developers have brought a number of FDA-approved point-of-care (POCT) and home self-tests to market.
These medical tests run the full spectrum. They include tests to detect HIV, malaria, pregnancy or male fertility, drug use or Hepatitis C. There are tests to monitor liver function, glucose in diabetics, cholesterol; and provide needle-free CBCs and genetic tests.
Portable Device Accurately Counts White Blood Cells
Pathologists and clinical laboratory managers may be particularly interested to learn that white blood cell counts (CBCs) is the goal for certain researchers. In fact, a collaboration of engineers at the California Institute of Technology (Caltech) in Pasadena, Calif., and LeukoDX, a Jerusalem-based medical technology firm, has developed a prototype for a portable POCT device. This device provides accurate, on-the-spot counts of the four major types of white blood cells. Details on this new device were reported in an article published in the April 7, 2013 issue of the journal Lab On a Chip.
White blood cells, or leukocytes, are the immune system’s primary defensive against infection and disease. Therefore, measuring the level of white blood cells in blood enables clinicians to easily detect and monitor various conditions.
There are five subtypes of white blood cells, which produce antibodies to fight organisms that invade the body:
Each serves a different function, which is why it’s useful to know the count for all of them. Lymphocytes attack specific viruses and bacteria, neutrophils combat bacteria; eosinophils target parasites and certain infections; monocytes respond to inflammation and replenish white blood cells in bodily tissue; and basophils—the rarest type—attack certain parasites.
The prototype POCT device developed by the researchers counts all five subtypes in a blood sample. It accurately differentiates between the four major subtypes, noted a Caltech press release that highlighted aspects of the scientific article. This POC system also could be used to identify abnormally high levels of the fifth subtype, basophils, which are too rare to accurately detect in clinical tests, noted the press release.
New Detection Assay Lights White Blood Cells to Identify Cell Subtypes
The new POCT device requires just a finger-stick blood sample. This specimen is treated with a new detection assay. It uses three dyes to stain white blood cells so they brightly emit light, or fluoresce, in response to laser light, noted the press release. The blood sample is treated with the dye assay before flowing through the microfluidic channel of the new device, which is small enough to ensure that only one white cell at a time can flow through the detection region. Each white blood cell is illuminated with a laser, causing it to fluoresce, with the resulting emission then split by a mirror into beams of green and red fluorescence.
White blood cell subtypes emit characteristic amounts of red and green light. The device generates highly accurate differential white blood cell counts by determining the intensity of emissions, explained the press release.
Pictured is a blood sample treated with a new dye assay developed by researchers at CalTech and LeukoDx. The sample flows through a microfluidic channel (lower left), providing fluorescence that enables a laser to count each of the four major subtypes of white blood cells (upper right) in blood. (Photo copyright Wendian Shi of Caltech.)
“The white blood cell counts from our new system closely match the results from tests conducted in hospitals and other central clinical [laboratory] settings,” stated Dr. Yu-Chong Tai, Caltech Professor of Electrical and Mechanical Engineering and the project’s principal investigator. “This could make point-of-care testing possible for the first time.”
POCT Device Could Monitor Cancer Patients at Home
The researchers noted extensive potential uses for portable while blood cell counters. They believe that the technology can improve outpatient monitoring of patients with leukemia and other cancers. It could also be used in combination with telemedicine to provide medical care to people in remote locations. It could even enable astronauts to evaluate their long-term exposure to radiation while still in space.
Yu-Chong Tai, Ph.D, (pictured) led the research team that developed a new detection assay that enables a point-of-care device to differentiate and count the four major white blood cell types in a drop of blood. He is both a Professor of Chemical and Mechanical Engineering at California Institute of Technology in Pasadena. (Photo copyright Caltech.)
“If we can give you a quick white blood cell count right in the doctor’s office, you can know right away if you’re dealing with a viral infection or a bacterial infection, and the doctor can prescribe the right medication,” noted Wendian Shi, Ph.D., a Microdevice Engineer and graduate student in Tai’s lab, who was lead author of the Lab on a Chip article.
Engineers Looking at Developing Handheld Device for Patient Use
Currently, a white blood cell count requires draw of a vial of blood, processing with large-scale clinical laboratory equipment and can take days to get back a result, noted Shi. This new POCT system only requires a drop of blood, fits into a small suitcase, and the result is immediate.
The engineers who developed the device, however, say it could easily be made into a handheld device. Shi said the ultimate goal is to create a home self-monitoring device. “For patients who struggle to find a balance between their treatment and their normal quality of life, we would like to offer a device that will help them monitor their conditions at home,” he noted. “It would be nice to limit the number of trips they need to make to the hospital for testing.”
POCT devices such as this can eventually be disruptive to clinical laboratories, as they are clinically accurate, less invasive, and provide quicker results at a lower cost than medical laboratories. Such devices, however, may become a valuable complement to the lab testing industry because it can shift tests with very low reimbursement out of centralized medical laboratories and into near-patient and home-test settings.
—Patricia Kirk
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Counting White Blood Cells at Home
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Hi Patricia, I notice on your last comment
“POCT devices such as this can eventually be disruptive to clinical laboratories, as they are clinically accurate, less invasive, and provide quicker results at a lower cost than medical laboratories.” For most POCT devices the cost per test is generally much higher due to the use of more consumable per test and higher reagent cost charge by vendor.