Development and psychometric evaluation of the assessment of self-injection questionnaire: an adaptation of the self-injection assessment questionnaire

Background Patient-reported outcome (PRO) instruments provide robust and effective means of evaluating patients’ treatment experience; however, none adequately cover experience using self-injection devices with enhanced features, such as an electromechanical autoinjector (e-Device). The aim of this study was to develop a PRO instrument that accurately assesses patient experience of using an e-Device and to evaluate its psychometric properties. Methods A mixed-methods approach was taken; two parallel, targeted literature reviews were conducted to identify relevant concepts and existing self-injection PRO instruments that could be adapted. Patient feedback obtained from two focus groups was used to inform initial instrument development. The pilot instrument was then administered in a multicenter, open-label, phase 3 clinical study in which patients self-injected certolizumab pegol using an e-Device, to gather evidence of its psychometric qualities. Exit interviews were conducted with a sub-sample of patients enrolled in the study to confirm the appropriateness and clarity of the items included and cognitively debrief the instrument. Confirmatory factor analysis (CFA) was conducted on all items, and each domain’s internal consistency was measured using Cronbach’s ɑ. Results The literature searches identified several e-Device-specific concepts related to device features, device function, side effects/reactions/pain, confidence, and interference/convenience in daily life. Seven existing PRO instruments were identified. The Self-Injection Assessment Questionnaire (SIAQ), containing pre- and post-injection questionnaire modules, was selected as most suitable and adapted using feedback from 19 patients in the two focus groups to form the pilot Assessment of Self-Injection (ASI) questionnaire. CFA resulted in some changes to the grouping of items in the post-injection module domains following psychometric evaluation of the ASI. Internal consistency was satisfactory for all pre- and post-injection domains (ɑ > 0.8). Cognitive debriefing results from 12 patient exit interviews confirmed the ASI’s appropriateness and clarity. Conclusions The ASI was developed iteratively with patient input and was evaluated in its intended clinical context of use. Psychometric analyses indicated promising cross-sectional results; the ASI was well understood and considered relevant by patients self-injecting using the e-Device, suggesting that it could be used in real-world settings to aid with clinical decision making. Trial registration: NCT03357471