‘Fun’ Sweat-measuring Sticker May Aid CF Diagnosis in Children

A soft skin sticker that can rapidly measure chloride levels in sweat, which are elevated in cystic fibrosis (CF) patients, may help avoid delays in diagnosis and treatment associated with current testing methods, especially in young children, a study reported. 

The so-called sweat sticker — which researchers said made young patients “smile and giggle” during testing — is expected to aid in diagnosing babies and children.

It also has the potential to monitor disease progression and response to treatment, the scientists said.

The study, “Soft, skin-interfaced sweat stickers for cystic fibrosis diagnosis and management,” was published in the journal Science Translational Medicine. 

CF is caused by mutations that lead to a deficiency in the CTFR protein, a channel in the cell membrane that regulates the movement of chloride ions in and out of cells, which is essential for mucus production, sweat, saliva, and tears. 

Within the first few days of life, newborns in the U.S. — and in Europe and many other nations — are screened for CF by a blood test. However, if the results are abnormal, clinicians usually measure chloride levels in sweat, which are higher in CF. 

The current sweat test requires babies to wear a hard, wrist-strapped device for up to 30 minutes, which can be difficult for smaller infants who have trouble producing enough sweat. In addition, a loose-fitting device is unable to collect a large enough sample. In such cases, the baby must have the test repeated, which may delay treatment.

“Some parents bring their baby in for testing and are sent home without a confirmed result because the device was unable to collect enough sweat,” Susanna McColley, MD, a pediatric pulmonologist at Lurie Children’s Hospital and Northwestern Medicine, in Illinois, said in a university press release.

“They go home without knowing if their baby has a serious disease or not, and their baby cannot yet start treatment. It can be agonizing,” said McColley, a study co-author.

A Northwestern University-led research team has now developed a soft, skin-mounted sticker that absorbs sweat and changes color based on chloride levels. It provides a fast, accurate, easy-to-read diagnosis of CF. 

Adhering directly to the skin without harsh adhesives, the thin, single-use sticker is more comfortable and imperceptible to the wearer, according to the team.

“Many labs encountered problems caused by the current collection methods, making this a frequent focus of quality improvement efforts,” said Shannon Haymond, PhD, former director of the clinical chemistry laboratory at Lurie Children’s and also a study author.

“I thought the flexible skin sensors could simplify the process and improve collection results. And because the sweat stickers are disposable and designed for single-use, they have an added advantage of preventing infection,” said Haymond, now Lurie Children’s vice chair for computational pathology and director of mass spectrometry.

The researchers validated the sticker in pilot studies involving CF patients and healthy volunteers across different age groups. 

The results showed the sweat stickers collected 33% more sweat compared to existing methods and demonstrated meaningful reductions in leakage rates. They “support further testing of the sweat stickers in larger studies,” the scientists wrote.

The sticker has tiny channels containing chemicals that change color in real-time based on the chloride concentration. Then, using a smartphone camera, users can snap a photo of the sweat-filled sticker and transmit it directly to a clinic for analysis, bypassing the need for expensive laboratory equipment and wait times, and avoiding diagnostic and treatment delays.

“By collecting and analyzing sweat at the point of collection, we can enable an earlier diagnosis,” said Tyler Ray, PhD, a postdoctoral researcher and the study’s first author.

“This is crucial for preventing severe complications and improving long-term patient outcomes,” Ray said.

The approach opens up the possibility of testing at home instead of in the clinical setting, which can help those who live in rural areas or without easy access to centers with specialized diagnostic tools. 

Additionally, the sticker could be used to track a CF patient’s long-term health and response to treatment in real-time. 

“Because this device is untethered, we plan to use it beyond clinical environments,” said Roozbeh Ghaffari, PhD, a research associate professor of biomedical engineering at Northwestern.

“In light of these new capabilities and further clinical validation, cystic fibrosis patients receiving treatment could someday use the sweat sticker at home to track their symptoms and hydration levels during daily living,” Ghaffari said.

For McColley, the test’s ease of use is the biggest game-changer.

“Children love stickers,” McColley said. “The sweat stickers made them smile and giggle. It’s a much easier, comfortable, and even fun device to wear.”