Wearable patch could help CF patients manage disease at home
Sensors monitor sweat chloride levels for physicians to evaluate remotely
Northwestern University scientists developed a wearable patch that could help cystic fibrosis (CF) patients manage their disease from home.
A study showed that the patch, developed in collaboration with scientists at Epicore Biosystems, measured sweat chloride in test participants as effectively as the gold standard method for sweat chloride assessment done in laboratories, according to a university press release.
“These findings highlight the promise of wearable biosensors in transforming remote disease management and optimizing personalized therapeutic strategies” for CF patients, the researchers wrote. They noted that the patch is not intended to replace traditional sweat chloride assessments.
The study, “Remote analysis and management of sweat biomarkers using a wearable microfluidic sticker in adult cystic fibrosis patients,” was published in Proceedings of the National Academy of Sciences.
A CF patient’s body produces abnormally thick, sticky mucus due to mutations in the CFTR gene, which contains instructions for cells to make a protein of the same name that controls the flow of water and salt molecules. In CF, dysfunction of the CFTR protein leads to abnormally high chloride levels in sweat. Measuring sweat chloride levels is the gold standard for diagnosing CF, and it can also serve as an indicator of CFTR protein functionality in response to treatment.
Patch offers an alternative to ‘cumbersome’ laboratory test
The standard way of measuring sweat chloride is to apply pilocarpine, a substance that can increase sweating, through the skin. A filter paper or gauze collects the sweat, which clinicians analyze in a lab using a process called chloridometry. “This technique is cumbersome and not suitable for remote settings or repeat measurements,” the researchers wrote.
The CF patch is soft and flexible and sticks to the skin on the forearm. It changes color depending on the level of chloride and the volume of sweat. Physicians can interpret the results using a smartphone application.
“We wanted to see how accurate our CF patch was relative to the gold standard, whether we could do it remotely at home, and then also see how consistent the sweat chloride is in response to the medications,” said Manu Jain, MD, a professor of medicine at Northwestern and the study’s senior author. “Are sweat chloride levels the same or very similar on a day-to-day basis, or is there a lot of variability … that could suggest that maybe these drugs are not working as optimally as they might otherwise?”
Twenty CF patients and seven healthy volunteers tested the device. The CF participants had an average age of 32.6, and all but one of them were being treated with CFTR modulators.
The researchers found strong correlations between chloride estimates using CF patch analysis and standard laboratory analysis in a clinic-based test. Results also showed strong associations between pilocarpine-induced and exercise-induced CF patch sweat chloride concentrations. This “demonstrates the potential for integrating exercise-induced sweat [chloride] testing into clinical monitoring protocols for [people with CF] on CFTR modulators,” the researchers wrote.
Participants then collected data at home using the patch after exercising to induce sweating. The measurements correlated strongly with in-clinic, exercise-induced CF patch measurements.
However, according to the team, the correlation was weaker in people with CF. The researchers said that could be related to higher day-to-day variability of sweat chloride in CF patients than in controls.
“Since pilocarpine-chloridometry and exercise laboratory CF Patch sweat [chloride] were measured on the same day, and CFTR modulators impact sweat chloride, this is consistent with the notion that CFTR modulators are contributing to more day-to-day variability of sweat [chloride] in PwCF,” the investigators wrote.
This also “highlights the limitations of assessing CFTR modulator efficacy and pharmacodynamics [effects of a drug on the body] based on a single in-laboratory chloridometry measurement,” they wrote.
Yet the study establishes the patch’s “potential as a noninvasive, real-time tool for assessing CFTR modulator efficacy, adherence, and pharmacodynamic variability,” the scientists said.
The technology might also one day help diagnose CF in low-resource areas, Jain said. “Potentially this could be used as a screening or diagnostic test in parts of the country where sweat testing is not readily available and could expedite the diagnosis of cystic fibrosis,” he said.
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