Summative Usability Evaluation of the SCTE-AI Device: A Novel Prefilled Autoinjector for Subcutaneous Testosterone Administration

Abstract

Background: The subcutaneous testosterone enanthate (TE) autoinjector (SCTE-AI) is a single-use, pre-filled, disposable autoinjector intended for testosterone (T) self-administration in adult males with T deficiency. Aim: To evaluate the usability of the market configuration of the SCTE-AI, including packaging and instructions for use (IFU), in order to identify and mitigate any preventable patterns of use errors that could result in harm. Methods: 4 groups of participants (injection-naïve or injection-experienced patients or caregivers) were randomized to 1 of 3 doses (50, 75, and 100 mg) of TE and either trained (ie, reviewed the IFU and shown how to properly inject) or not trained (only given the IFU). After simulated at-home use, participants were asked questions regarding the comprehensibility of the IFU and the intuitiveness/usability of the device. All tasks were measured as success, use error, or close call (participant initiated an error but recovered in time). Main Outcome Measure: Usability (success rates, errors, and close calls) of the drug/device combination by adult males with T deficiency or their caregivers. Results: 65 patients received 1 dose of TE, and 59 patients received 2 doses. Overall, 99 of 123 (80.5%) attempted injections resulted in administration of 1 full dose. Injection success rates were high and comparable among the various user groups. The most common use error (21 of 24) was due to not holding the autoinjector on the abdomen long enough (at least 8 seconds). Few critical drug delivery and safety errors or close calls were observed. No unmitigated use errors by patients or caregivers were apparent that could result in harm or have a negative impact on treatment. SCTE-AI was well tolerated. Clinical Implications: The SCTE-AI development process resulted in a subcutaneous, TE autoinjection device that is intuitive to use, with clear labeling and packaging and an easy-to-understand IFU, providing an option for T-deficient adult males to self-inject subcutaneously at home. Strength & Limitations: The strengths of the study include use of a patient-ready drug/device combination for self-administration and inclusion of both injection-naïve and injection-experienced patients and caregivers. The main limitation of the study is the presence of observers/cameras that may have distracted or created performance anxiety, potentially contributing to errors. Conclusion: Results of this usability validation study indicate that the SCTE-AI device is safe and intuitive to use, with a low potential for harm and is associated with a high rate of injection success, regardless of prior training or experience.

Autoinjector Design Parameters: A Human Factors Perspective

“…Further, it is also evident that there are few studies done to systematically investigate technical attributes of autoinjectors with respect to specific user characteristics and populations. Published literature on autoinjectors are typically limited to either characterization of autoinjector performance (i.e., engineering tests) (Schwirtz & Seeger, 2010) or in the context of usability evaluations, ease of use, or preferences (Arora et al, 2018;Hudry et al, 2017;Kivitz et al, 2018;Wray et al, 2018) for specific intended patient groups, on specific autoinjector designs. However, there is a gap in understanding objective measures (e.g., force limitations) of potential users with varying characteristics such as age, gender, dexterity limitations, etc.…”

Formative and Validation Human Factors studies of a new disposable autoinjector for subcutaneous delivery of chronic disease therapies

“…Finally, with autoinjector devices a final common use error was reported, which was the failure to continue holding the device in place for a few additional seconds after the end of injection [22,24,25]. Although the risk of underdosing is very limited when removing the device immediately after the second click, it is also dependent on the drug being used and this risk may need to be evaluated through clinical studies.…”

“…In the next formative and validation studies, the IFU was provided with the autoinjector and was free to read or not, to mimic real-life. As, previous studies demonstrated that, from the first use, a training on how using the device minimized use error ratings [22]. During the validation, a subgroup of participants received a training.…”

“…Safe, effective, easy to use, and satisfactory autoinjectors have been developed since the 1990s to improve injection experience, and thereby improve patient adherence to therapy [13][14][15][16][17][18]. Human Factor evaluations are thus essential to inform and assess the design of devices throughout the entire design and development process to ensure effective, efficient, and safe use by minimizing potential use errors and resulting harm [5,[19][20][21][22][23][24][25][26].…”