Evaluation of the Tolerability of a Steel Needle and an Adhesive for a Patch Pump

Insulin infusion sets play a significant role in patient safety and insulin pump acceptance. There are 2 types of insulin catheters (steel and Teflon) attached to the end of the IIS to transfer the insulin into the subcutaneous tissue, with Teflon catheters commonly used in patch pumps. To assess the feasibility of a steel catheter in a patch pump, a steel needle and an adhesive were tested for tolerability and wear comfort over several days by patients with diabetes.^1,2

This study was performed with 20 adult people with diabetes (35% type 1, 65% type 2) on multiple daily injections (MDIs, 65%) or insulin pump therapy (35%) in March 2019 at the Institut für Diabetes-Technologie, Forschungs- und Entwicklungsgesellschaft mbH an der Universität Ulm, Germany. The study was approved by the ethics committee and the responsible authority; principles of good clinical practice were followed.

A nonfunctional mock-up patch-pump system (size = 2.8 × 1.8 × 0.7 inch; weight = 72 g) combined a commercially available sterile 0.5-inch 29-gauge insulin pen steel needle (Insupen 29G Pic solution, Pikdare S.p.A., Casnate con Bernate, Italy) and an adhesive (4076 SC Spunlace Extended Wear Nonwoven Tape, 3M^TM, St. Paul, MN) was worn by the patients for 5 days (i.e., on 6 calendar days). No drug application was possible with the system.

Participants rated the pain and itching at the insertion site of the needle, as well as wear comfort and pain when changing needle position, on a 100-mm visual analog scale (VAS, see Figure 1). In a similar approach, participants rated the size and weight of the mock-up, size of the adhesive and adhesive strength on a 5-point Likert scale (LS) according to the FDA draft guidance (see Figure 1). ³ The questionnaires were designed specifically for this study and had not been validated.

Figure 1.

Visual analog scales (VAS) for pain, itching, wear comfort, and pain by change of needle position (simulated bolus delivery) across 6 calendar days, and 5-point Likert scales (LS) for size of the mock-up, weight of the device, size of the adhesive, and adhesive bond strength after 5 days of use.

VAS allowed ratings between 0 (very good) and 100 (very poor), and ratings were grouped into 5 categories (0-20, 21-40, 41-60, 61-80, and 81-100). The Likert scale ranged from 1 (very good) to 5 (unsatisfactory).

Wear comfort and adhesive strength during different types of daily activities (daily routine, shower, physical labor, physical activity, work at desk/PC, sleep) were rated favorably (median 2 and 1 on a 5-point LS, respectively). Additional fixation was used by one participant on day 2 after showering, when approximately 25% of the adhesive area had lifted according to the participant’s reports. The other 19 adhesives were rated to have 100% adherence (13), ≥90% to <100% adherence (4), or ≥75% to <90% adherence after 5 days (2).

During the study, 5 adverse events occurred with the study system, all of which were mild skin reactions. Three hematomas were related to the steel needle, 1 case of itching and 1 erythema were related to the adhesive. All events resolved without sequelae within 2 to 7 days.

The mock-up did not deliver insulin, although some infusion site issues are likely exacerbated by the presence of insulin. ⁴ Furthermore, a comparator device or control group might have helped account for potential differences in ratings between MDI and pump users.

This feasibility evaluation demonstrated good tolerability and wear comfort of both the steel needle and the adhesive in patients with diabetes for up to 5 days (120 hours). The adhesive bond strength was sufficient for a 5-day use.