(186) Pilot Study of Sweat Induction Using Pilocarpine Microneedles During Sweat Test in Healthy Adults Without Cystic Fibrosis

Background: The Sweat Test using pilocarpine iontophoresis remains the gold standard for diagnosing Cystic Fibrosis (CF), but access and reliability are limited by the need for specialized equipment and training, as well as higher rates of inadequate sweat collection among infants and young children. These shortcomings can lead to delays in diagnosis and initiation of therapies for CF. The response and adherence to CFTR modulators can also be monitored with sweat testing. However, limitations of the current method of sweat testing do not permit its use as a point-of-care test.

Methods: We created a simplified method for sweat testing that eliminates the equipment and complexity of iontophoresis by developing a skin patch containing solid microneedles made of pilocarpine. Pressing the patch to the skin is intuitive and painless, and the microneedles rapidly dissolve in the skin to induce sweating, followed by the conventional sweat collection procedure using Macroduct collectors. We conducted a non-randomized clinical trial among

healthy human subjects (clinicaltrials.gov - NCT04732195) with pilocarpine microneedle patches on one forearm and pilocarpine iontophoresis on the other forearm. Sweat volume and sweat chloride concentration were measured in the collected samples from each method. Macroduct collectors were weighed before and after the collection of sweat to calculate total sweat output. Subjects were also monitored for any pain or discomfort during testing using a standardized pain score, and skin erythema at the site of application was quantified for each method using a validated erythema assessment scale.


Results: A total of 50 paired sweat tests were conducted in 16 males and 34 females between 19-61 years of age. There were 22 Caucasian, 12 Asian, 7 African American and 9 Hispanic participants. There were 2 sweat tests (both Asian) where no sweat was produced by either method. The total sweat volume collected in the remaining 48 sweat tests was not significantly different for the iontophoresis method (mean 43.8 g, 95% Confidence Interval 34.6-53.0 g) and microneedle patch method (mean 41.20g, [34.08-48.32]) (p=0.4737). The total amount (mean +standard deviation) of pilocarpine delivered into the skin from the microneedle patches was 1.09+0.43 mg, which was not significantly different from the 1.18+0.66 mg pilocarpine delivered by iontophoresis (p=0.6628). Overall, the subjects tolerated the procedures well, with no significant increase in pain or erythema noted at the site of testing for the microneedle patch method when compared to iontophoresis method.

Conclusions: Compared to the standard of care pilocarpine iontophoresis method, the pilocarpine microneedle patch method for sweat testing provided a similar amount of pilocarpine delivered to the skin and a comparable sweat output. Further studies are being planned in CF subjects to further validate this method. Further innovations in the sweat testing technique could allow at-home monitoring and as a point-of-care test in clinic.

Acknowledgements: This study was funded by Emory University's Center for Cystic Fibrosis and Airway Disease Research; Children's Healthcare of Atlanta, Grant/Award Number: #00086859.

US Provisional Patent Application Number – 63/132,086 - Patent Pending.

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