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

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: α = 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.