Development of an instrument for patient-reported outcomes in Thai patients with type 2 diabetes mellitus (PRO-DM-Thai)

Abstract

Background: Effectiveness of self-care and treatment of diabetes mellitus depends upon patient awareness of their own health and disease outcomes. Physician decisions are improved by insight into patient perspectives. Objective: To develop an instrument for patient-reported outcomes in Thai patients with type 2 diabetes mellitus (PRO-DM-Thai). Methods: The study consisted of: (1) content development using a literature review and in-depth interviews of providers and patients, and validity testing using a content validity index (CVI); (2) construct validity and reliability testing by confirmatory factor and Cronbach's α analyses of data from a cross-sectional descriptive survey of 500 participants from May to June, 2011; and, (3) criterion-related validity from a cross-sectional analytical survey of 200 participants from September to November, 2011. Results: PRO-DM-Thai passed all of the validity tests. The instrument comprises seven dimensions and 44 items, including physical function, symptoms, psychological well-being, self-care management, social well-being, global judgments of health, and satisfaction with care and flexibility of treatment. The CVI at the item-level (I-CVI) were between 0.83 to 1.00 and the scale-level average agreement (S-CVI/Ave) was 0.98. All dimension models had overall fit with empirical data, while the hypothesized model demonstrated a good fit (χ2 = 5.23; (df = 6), P > 0.05, AGFI = 0.986, RMSEA = 0.000). Cronbach's α for the total scale was 0.91 and for the subscales was 0.72-0.90. The total scores effectively discriminated groups of patients with different levels of disease control. Conclusion: PRO-DM-Thai showed satisfactory levels of validity and reliability when applied to Thai diabetic patients.