During chemotherapy, a sharp drop in white blood cells leaves patients vulnerable to dangerous infections. In the US, one in six chemo patients is hospitalized with an infection—and about 7 percent of those infections prove fatal. Infected patients also have to miss their next chemotherapy dose, which sets back their cancer treatment.  

A team of researchers from MIT and the Technical University of Madrid, led by Research Laboratory of Electronics postdoc Carlos Castro-Gonzalez, has now developed a portable white-blood-cell monitor. The device could be used at home, without taking blood samples, to determine whether prophylactic antibiotics and drugs that promote growth of white blood cells are needed to ward off infections.

The tabletop prototype records video of blood cells flowing through capillaries just below the skin’s surface at the base of the fingernail. These capillaries are so narrow that white blood cells must squeeze through one at a time. That makes it easier for them to be seen by a wide-field microscope that emits blue light, which penetrates about 50 to 150 micrometers below the skin and is reflected back to a video camera.

In tests, three human assistants watched one minute of such video for each of 11 chemotherapy patients. They detected with 95 percent accuracy whether a patient’s white-cell levels were above or below the threshold of danger. The researchers have since developed a computer algorithm using AI and machine vision that can perform the same task automatically.

They’ve also launched Leuko, a startup that’s commercializing the technology.