Development and factor analysis of a questionnaire to measure patient satisfaction with injected and inhaled insulin for type 1 diabetes

OBJECTIVE - To develop a self-administered questionnaire to address alternative delivery routes of insulin and to investigate aspects of patient satisfaction that may be useful for subsequent assessment and comparison of an inhaled insulin regimen and a subcutaneous insulin regimen. RESEARCH DESIGN AND METHODS - Attributes of patient treatment satisfaction with both inhaled and injected insulin therapy were derived from five qualitative research studies to arrive at a 15-item questionnaire. Each item was analyzed on a five-point Likert scale so that higher item scores indicated a more favorable attitude. There were 69 subjects with type 1 diabetes previously taking injected insulin therapy who were enrolled in a phase II clinical trial. Their baseline responses on the questionnaire were evaluated and subjected to an exploratory factor analysis. Meaningful factors were retained and interpreted based on their psychometric properties. RESULTS - Exploratory factor analysis suggested a two-factor solution accounting for 66 and 20% of the variance, respectively. The first factor contained 10 reliable items (Cronbach's alpha = 0.89) relating to convenience and ease of use, and the second contained 5 reliable items (Cronbach's alpha = 0.82) relating to social comfort. CONCLUSIONS - Among patients with type 1 diabetes, this analysis highlighted and quantified two key factors contributing to patient satisfaction: convenience/ease of use and social comfort. The questionnaire underwent rigorous development, had reliable properties, and an interpretable and rich factor structure. This report is intended to help advance, in subsequent investigations, the understanding and measurement of treatment satisfaction with novel and existing forms of insulin delivery.