Background: Inflammatory bowel disease (IBD) monitoring currently relies on patient reported symptoms or cross-sectional assessments of blood, stool, imaging or endoscopy. Advances in wearable technology provide a novel means to monitor IBD activity in real time, remotely and passively. Sweat is an easily accessible biofluid for continuous sampling of analytes, including inflammatory markers and cytokines. We evaluated a sweat sensing wearable device in subjects with and without IBD to pilot the feasibility of measuring disease relevant markers continually and passively over time.

Methods: Participants, ≥ 18 years of age, with an IBD related hospital admission and a C-reactive protein > 5 ug/L wore a sweat sensing wearable device for up to 5 days. Tumor necrosis factor-alpha (TNF-α) levels were continually assessed in the sweat via the sensor. The immunoassay on the sweat sensor was developed by immobilizing a specific capture probe antibody to capture TNF-α in sweat. Data was transmitted from the device via Bluetooth to the cloud server. Sensor response was measured using impedance spectroscopy. Serum samples were collected daily. Blood was drawn daily to assess serum TNF-α levels. The linear correlation coefficient was calculated between sweat and serum TNF-α values. A second cohort of healthy subjects without any chronic diseases wore the sweat sensing device for up to 48 hours. A t-test (α=0.05) was used to determine whether the sweat TNF-α concentrations differed between subjects with and without IBD.

Results: Twenty-eight subjects were enrolled (Table 1). The SWEATSENSOR device measured sweat TNF-α in subjects with IBD in the range of 0.31 to 4.1 pg/mL, and in healthy controls in the range of 0.09 to 1.23 pg/mL. In the 16 subjects with IBD, a linear relationship between serum and sweat TNF-α levels was observed (R²=0.72). Subjects with IBD were found to have a mean sweat TNF-α level of 2.11 pg/mL, compared to a mean value of 0.19 pg/mL in 12 healthy controls (p<0.0001) (Figure 1). Sweat TNF-α measurements differentiated subjects with active IBD from healthy subjects with an AUC of 0.962 (95% CI: 0.894 to 1.000) and a sensitivity and specificity of 90.9% and 91.7% at a TNF-α cutoff of 0.98 pg/mL.

Conclusion: A sweat sensing wearable device can longitudinally assess key sweat-based markers of IBD. TNF-α levels in the sweat of subjects with IBD correlate with serum values, suggesting feasibility in non-invasive disease monitoring. This work suggests the feasibility of using a non-invasive sweat-sensing wearable device to monitor IBD disease activity.

Table 1. Characteristics of subjects with inflammatory bowel disease.

Figure 1. Temporal plots of sweat TNF-α levels. (A) Sweat TNF-α levels are plotted at 1-minute intervals in subjects with IBD (red) and healthy controls (blue). Each line represents a subject’s sweat values over the follow up period. (B) The mean sweat TNF-α level for the cohort of subjects with IBD (red) and healthy controls (blue) over the follow up period.

Sarah Shahub

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