Monitor detects low white blood cell levels

Their tabletop prototype records video of blood cells flowing through capillaries just below the surface of the skin at the base of the fingernail. A computer algorithm can analyse the images to determine if white blood cell levels are below the threshold that doctors consider dangerous.

“Our vision is that patients will have this portable device that they can take home, and they can monitor daily how they are reacting to the treatment. If they go below the threshold, then preventive treatment can be deployed,” says Carlos Castro-Gonzalez, a postdoc in MIT’s Research Laboratory of Electronics (RLE) and the leader of the research team.

In a paper appearing in Scientific Reports, the researchers showed that the device could accurately determine whether white blood cell levels were too low, in a study of 11 patients undergoing chemotherapy.

The paper’s first author is Aurélien Bourquard, an RLE postdoc. Other team members who developed the new technology include RLE research engineer Ian Butterworth, former MIT postdoc Alvaro Sanchez-Ferro, and Technical University of Madrid graduate student Alberto Pablo Trinidad.

The researchers began this project nearly four years ago as part of the Madrid-MIT M+Vision Consortium, which is now part of MIT linQ. The program draws postdocs from around the world to try to solve problems facing doctors and hospitals. In this case, the research team visited the oncology department of a Madrid hospital and found that low white cell levels in patients were making them susceptible to life-threatening infections.

Chemotherapy patients usually receive a dose every 21 days. After each dose, their white blood cell levels fall and then gradually climb again. However, doctors usually only test patients’ blood just before a new dose, so they have no way of knowing if white blood cell levels drop to dangerous levels following a treatment.

“In the U.S., one in six chemotherapy patients ends up hospitalised with one of these infections while their white cells are particularly low,” Castro-Gonzalez says. Those infections lead to long, expensive hospital stays and are fatal in about 7 percent of cases. The patients also have to miss their next chemotherapy dose, which sets back their cancer treatment.

The MIT team estimated that if there were a way to detect when patients’ white cell counts went below the threshold level, so they could be treated with prophylactic antibiotics and drugs that promote white blood cell growth, about half of the 110,000 infections that occur in chemotherapy patients in the United States every year could be prevented.

The technology the researchers used to tackle this problem consists of a wide-field microscope that emits blue light, which penetrates about 50 to 150 microns below the skin and is reflected back to a video camera.

The researchers decided to image the skin at the base of the nail, known as the nailfold, because the capillaries there are located very close to the surface of the skin. These capillaries are so narrow that white blood cells must squeeze through one at a time, making them easier to see.

The technology does not provide a precise count of white blood cells, but reveals whether patients are above or below the threshold considered dangerous — defined as 500 neutrophils (the most common type of white blood cell) per microliter of blood.

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Image credit: MIT.