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

Abstract

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.