Evaluating the reliability, validity and minimally important difference of the Taiwanese version of the diabetes quality of life (DQOL) measurement.

BACKGROUND: Few diabetes HRQOL instruments are available in Chinese language. We tested psychometric properties of a Diabetes Quality of Life (DQOL) in Chinese language for diabetes patients in Taiwan and estimated its minimally important differences (MIDs). METHODS: Data were collected from 337 patients treated in diabetes clinics of a Taiwan teaching hospital. Pearson's correlations among domain scores of the DQOL (satisfaction, impact, and worry), the D-39S (a diabetes-specific instrument, including domains of diabetes control, energy and mobility, social burden and anxiety and worry, and sexual functioning) and the RAND-12 (a generic instrument, including physical health composite (PHC) and mental health composite (MHC)) were estimated to determine convergent/discriminant validity. Known-groups validity was examined using 2-hour postprandial plasma glucose (2 h PPG), hemoglobin A1c (HbA1c)) and presence of complications (retinopathy, neuropathy, and diabetic foot complications rather than the known groups of cardiovascular and cerebrovascular complications). We used a combined anchor- and distribution-based approach to establish MIDs. RESULTS: The DQOL scores were more strongly correlated with the physical domains of the D-39S (diabetes control and energy and mobility) and RAND-12 PHC than psychological domains of the D-39S (social burden, anxiety and worry, and sexual functioning) and RAND-12 MHC. The DQOL showed satisfactory discriminative ability for the known groups of 2 h PPG and HbA1c (effect size (ES) > or = 0.2) and retinopathy, neuropathy, and diabetic foot complications (ES > or = 0.3), but less satisfactory for the known groups of cardiovascular and cerebrovascular complications. MIDs for the DQOL domains were 3-5 points for satisfaction, 4-5 points for impact, 6-8 points for worry, and 3-4 points for overall HRQOL. CONCLUSION: We validated a DQOL in Chinese language for diabetes patients in Taiwan and provided MIDs to facilitate the measure of diabetes HRQOL.

Diabetes-specific or generic measures for health-related quality of life? Evidence from psychometric validation of the D-39 and SF-36.

OBJECTIVE: There is a debate regarding the use of disease-specific versus generic instruments for health-related quality of life (HRQOL) measures. We tested the psychometric properties of HRQOL measures using the Diabetes-39 (D-39) and the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). METHODS: This was a cross-sectional study collecting data from 280 patients in Taiwan. Exploratory factor analysis was conducted to evaluate construct validity of the two instruments. Known-groups validity was examined using laboratory indicators (fasting, 2-hour postprandial plasma glucose, and hemoglobin A1c), presence of diabetic complications (retinopathy, nephropathy, neuropathy, diabetic foot disorder, cardiovascular and cerebrovascular disorders), and psychosocial variables (sense of well-being and self-reported diabetes severity). Overall discriminative power of the two instruments was evaluated using the C-statistic. RESULTS: Three distinct factors were extracted through factor analysis. These factors tapped all subscales of the D-39, fourphysical subscales of the SF-36, and four mental subscales of the SF-36, respectively. Compared with the SF-36, the D-39 demonstrated superior known-groups validity for 2-hour postprandial plasma glucose groups but was inferior for complication groups. Compared with the SF-36, the D-39 discriminated better between self-reported severity known groups, but was inferior between well-being groups. In overall discriminative power, the D-39 discriminated better between laboratory known groups. The SF-36, however, was superior in discriminating between complication known groups. CONCLUSIONS: For psychometric properties, the D-39 and the SF-36 were superior to each other in different regards. The combined use of a disease-specific instrument and a generic instrument may be a useful strategy for diabetes HRQOL assessment.