Dose Accuracy, Injection Force, and Usability Assessment of a New Half-Unit, Prefilled Insulin Pen

This study examines the utility of the first prefilled, rapid-acting insulin pen that can be dialed in half-unit increments. Dose accuracy and injection force were examined through a series of design-verification tests, and usability was established by human factors validation testing.

Devices were tested for dose accuracy at 3 different doses and temperatures and under free fall, vibration, and cold storage conditioning. Injection force was measured at the maximum dose (30 units). Both experiments used the same semiautomated testing system. Usability was validated in a human factors simulated-use study that included 60 participants (patients with type 1 or type 2 diabetes [aged 10-79 years], adult caregivers, and health care providers).

The pen met the International Organization for Standardization (ISO) 11608-1:2014 requirements for dose accuracy at all settings and conditions tested. Furthermore, all individual results were within the ISO specification limits. Mean injection force across temperature settings ranged from 9.25 to 10.85 N at the highest dose. The usability validation study confirmed that use-related risks were reduced to the extent possible and that additional modifications were not likely to afford further reductions.

The results from these studies demonstrated accurate dosing over the dose range (0.5-30 units) at different temperatures and conditions with an injection force that should accommodate the intended users. Use safety and usability in patients with diabetes, caregivers, and health care professionals were validated. The added convenience of this new half-unit, prefilled pen may ease the burden of diabetes management for patients who require smaller incremental dosing.