Generic and diabetes-specific well-being in the AT.LANTUS Follow-on study: Further psychometric validation of the W-BQ28 indicates its utility in research and clinical practice in Type 2 diabetes in the UK
Speight, J.; Khagram, L. A.; Davies, M. J.
Aims To undertake further psychometric validation of the W-BQ28 to determine its suitability for use in adults with Type 2 diabetes in the UK using data from the AT.LANTUS follow-on study. Methods A total of 353 people with Type 2 diabetes participated in the AT.LANTUS Follow-on study, completing measures of well-being (W-BQ28), treatment satisfaction (DTSQ) and self-care (SCI-R). Confirmatory factor analyses was used to confirm the W-BQ28 structure and internal consistency reliability was assessed. Additional statistical tests were conducted to explore convergent, divergent and known-groups validity. Minimal important differences were calculated using distribution and anchor-based techniques. Results Structure of the W-BQ28 (seven four-item subscales plus 16-item generic and 12-item diabetes-specific scales) was confirmed (comparative fit index=0.917, root mean square error of approximation (RMSEA)=0.057). Internal consistency reliability was satisfactory (four-item subscales: alpha=0.73-0.90; 12/16-item scales: alpha=0.84-0.90). Convergent validity was supported by expected moderate to high correlations (rs=0.35-0.67) between all W-BQ28 subscales (except Energy); divergent validity was supported by expected low to moderate correlations with treatment satisfaction (rs=-0.03-0.52) and self-care (rs=0.02-0.22). Known-groups validity was supported with statistically significant differences by sex, age and HbA1c for expected subscales. Minimal important differences were established (range 0.14-2.90). Conclusions The W-BQ28 is a valid and reliable measure of generic and diabetes-specific well-being in Type 2 diabetes in the UK. Confirmation of the utility of W-BQ28 (including establishment of minimal important differences) means that its use is indicated in research and clinical practice. 2012 Diabetes UK.