title: 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.
abstract: OBJECTIVE
  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 (r(s) = 0.35-0.67) between all W-BQ28 subscales (except Energy); divergent validity was supported by expected low to moderate correlations with treatment satisfaction (r(s) = -0.03-0.52) and self-care (r(s) = 0.02-0.22). Known-groups validity was supported with statistically significant differences by sex, age and HbA(1c) 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.
authors.affiliation: AHP Research, Hornchurch, UK. jane.speight@ahpresearch.com
authors.forename: J
authors.initials: J
authors.lastname: Speight
authors.forename: L A
authors.initials: LA
authors.lastname: Khagram
authors.forename: M J
authors.initials: MJ
authors.lastname: Davies
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000523:psychology* / Q000628:therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D017060:Patient Satisfaction; D011594:Psychometrics / Q000379:methods*; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D012648:Self Care / Q000523:psychology; D006113:United Kingdom / Q000453:epidemiology