Psychometric evaluation of the Satisfaction with Oral Anti-Diabetic Agent Scale (SOADAS)

In this study we developed and evaluated the psychometric properties of the Satisfaction with Oral Anti-Diabetic Agent Scale (SOADAS), the first treatment satisfaction instrument specific to oral anti-diabetic agents (OADs). Three focus groups and three rounds of cognitive debriefing interviews with type 2 diabetes patients using OADs informed the development of the six-item SOADAS. The measurement properties of the SOADAS were evaluated in a US cross-sectional study. Patients completed the SOADAS, Treatment Satisfaction for Medication Questionnaire (TSQM), the Short Form-12 (SF-12) Health Survey and a demographic questionnaire. The first half of the recruited patient population was asked to return at 7 days follow-up to complete the SOADAS again. An exploratory factor analysis on the SOADAS yielded a one-factor solution, indicating that the SOADAS was uni-dimensional. The SOADAS had high internal consistency reliability (Cronbach's alpha=0.86) and acceptable test-retest reliability (ICC=0.79). It was correlated most highly with the TSQM (r=0.71, p<0.001) and least with the mental summary component score of the SF-12 (r=0.24, p=0.014). Mean SOADAS scores were approximately two points higher for participants with lower HbA(1c) values (<7%) versus those with higher values, and for participants without versus with selected symptoms (p<0.05). The findings from this study suggest that the SOADAS is a valid and reliable measure of patient satisfaction with oral anti-diabetic medications. This questionnaire may be useful for assessing outcomes in future clinical studies of oral anti-diabetic medications.