Intuitiveness, ease of use, and preference of a prefilled growth hormone injection pen: a noninterventional, randomized, open-label, crossover, comparative usability study of three delivery devices in growth hormone-treated pediatric patients

Abstract

Background: Growth hormone (GH) is used to treat pediatric and adult GH deficiency (GHD) and growth failure in, among others, patients with Turner syndrome or children born small for gestational age. To improve treatment adherence, self-injection devices should be easy to learn, easy to use, and well accepted, especially in pediatric patients. Several GH pen devices are available, each with distinct features designed for specific patient needs.

Objectives: This study compared injection time and intuitiveness of a prefilled test injection device (Norditropin FlexPro, Novo Nordisk A/S, Bagsværd, Denmark) with those of 2 commercially available durable injection devices (easypod, Merck Serono SA, Geneva, Switzerland; and Genotropin, Pfizer Inc, New York, New York) in GH-treated pediatric patients. Dose accuracy, application errors, intuitiveness, usability, device features, ease of learning, ease of use, and overall preference were also assessed.

Methods: This noninterventional, randomized, open-label, crossover study enrolled patients aged ≥10 to <18 years who were diagnosed with GHD or Turner syndrome or were born small for gestational age. Patients were allocated to an intuitiveness group (without instruction) or an instruction group and assigned to 1 of 3 sequences of device testing. For each device, time taken to deliver a mock injection of test medium (FlexPro) or GH (easypod and Genotropin) into an Eppendorf tube and the delivered dose were measured. Dose accuracy and application errors were assessed by a health care professional. Patients assessed the intuitiveness (intuitiveness group only), device features, ease of learning, ease of use, and overall preference of the devices using questionnaires.

Results: Included in the study were 56 patients (mean [SD] age, 13.6 [2.1] years; 63% male; GHD, 44 patients; Turner syndrome, 3; born small for gestational age, 9): 30 in the intuitiveness group and 26 in the instruction group. In the intuitiveness group, the mean (SD) mock injection time was significantly shorter with FlexPro (47.0 [49.0] seconds) than with the easypod (219.2 [72.6] seconds; P < 0.001) or the Genotropin pen (95.1 [78.4] seconds; P < 0.01). In the instruction group, injection time was also shortest with FlexPro (30.7 [10.8] seconds vs 59.6 [13.1] with easypod and 40.7 [18.6] with the Genotropin pen; both, P < 0.001). Most patients (70%) ranked FlexPro as the most intuitive device (easypod, 0%; Genotropin, 30%). In both the intuitiveness and instruction groups, a significantly greater proportion of patients considered FlexPro easiest to learn compared with the easypod and Genotropin devices (both, P < 0.001), although more patients preferred the easypod or Genotropin devices than FlexPro with regard to appearance (intuitiveness group: FlexPro, 8 patients; easypod, 9; and Genotropin, 13; instruction group: FlexPro, 4; easypod, 10; and Genotropin, 12) and quality (intuitiveness group: FlexPro, 6 patients; easypod, 10; and Genotropin, 14; instruction group: FlexPro, 8; easypod, 12; and Genotropin, 6), and easy- pod's delivery feedback feature was preferred by more patients (intuitiveness group: FlexPro, 8 patients; easypod, 14; Genotropin, 8; instruction group: FlexPro, 8; easypod, 14; and Genotropin, 4). Dose accuracies (as assessed by weighing the delivered dose and calculating variation in the delivered dose by device) were 4.6% with FlexPro, 14.6% with easypod, and 20.6% with the Genotropin pen in the intuitiveness group, and 2.7% with FlexPro, 5.8% with easypod, and 24.4% with the Genotropin pen in the instruction group.

Conclusion: In this study, Norditropin FlexPro was associated with shorter injection times, higher dose accuracy, and greater intuitiveness, and was rated as easier to learn compared with the easypod and Genotropin devices.