Akhil Padmanabha, a Ph.D. student in Carnegie Mellon University's Robotics Institute, helped invent a wearable device that can objectively measure the intensity of scratching and evaluate the efficacy of medications meant to reduce itching.

A new wearable device may objectively measure the intensity of scratching.

Akhil Padmanabha, a PhD student in Carnegie Mellon University's (CMU) Robotics Institute helped invent a wearable device that can measure the intensity of scratching and evaluate the efficacy of medications meant to reduce itching.

"I stumbled upon a paper on wearables for scratch detection," says Padmanabha, who recalled that though the device could detect when and how long someone scratched, it was missing a critical component of scratching — intensity. "We really wanted to quantify that intensity of scratching."

Working with Sonal Choudhary, MD, a dermatologist and dermatopathologist at the University of Pittsburgh School of Medicine and his CMU advisors — Zackory Erickson, assistant professor of robotics, and Carmel Majidi, the Clarence H. Adamson Professor of Mechanical Engineering,  Padmanabha devised a device that could be worn like a ring on a scratching finger.

Like previous detection devices, it used an accelerometer to measure finger movement. But while accelerometers can detect some vibrations, they can't pick up the high-frequency ones most associated with scratching. To measure these, the researchers also incorporated a contact microphone, which proved to be key in measuring intensity. The microphone doesn't sense audio. Instead, it detects high-frequency vibrations through solid objects, such as a finger.

"When you're scratching, your finger is actually vibrating," Padmanabha explains in a news release.

Because the contact microphone can't detect normal sound, its use doesn't pose a privacy concern when worn in public.

The team developed algorithms for the device using data from healthy volunteers who wore it while scratching a pressure-sensitive tablet. The tablet then estimated the scratch intensity in milliwatts. A machine learning algorithm then correlated the raw input from the sensor with the scratch intensity estimates from the tablet. They then converted the scratch intensity to a 0-10 scale that physicians use in practice.

In clinical studies, a change of four units on the 0-10 scale, as reported subjectively by patients, is considered clinically important, Padmanabha says. The researchers demonstrated that their device had a mean absolute error of 1.37, indicating a precision that would make its readings clinically significant.

They also showed, for the first time, that patients' subjective estimations on the 0-10 scale often markedly differ. For instance, scratch intensity reported by one patient as a 10 might be the equivalent of another patient's four.

Choudhary, also an assistant professor of dermatology at UPMC, adds that once it has been further validated, the device would be most useful to researchers who are testing new drugs and need to precisely determine if they affect itching. It will likely be of less use in clinical medicine, she says, where doctors are used to questioning their patients about their itching symptoms.

But Padmanabha hopes that the device also might be used by doctors and, if not, at least by patients themselves. He is now seeking research funding to continue work on the device.

The research appears in Communications Medicine.

CAPTION: Robotics Institute Ph.D. student Akhil Padmanabha helped invent a wearable device that can objectively measure the intensity of scratching. Such a device could help researchers better evaluate the efficacy of medications meant to reduce itching.

CREDIT: Carnegie Mellon University