title: Head-to-head comparisons of quality of life instruments for young adult survivors of childhood cancer.
abstract: OBJECTIVE
  Few studies examine the relevance of health-related quality of life (HRQOL) instruments for young adult survivors of childhood cancer (YASCC). This study compared the psychometric properties of two survivor-specific instruments, the Quality of Life-Cancer Survivor (QOL-CS) and Quality of Life in Adult Cancer Survivor (QLACS).
  
  
  METHODS
  Data from 151 YASCC who enrolled in cancer/tumor registries of two medical centers were used. We examined construct validity by conducting confirmatory factor analysis using indices of chi-square statistic, comparative fit index, and root mean square error of approximation. We examined convergent/discriminant validity by comparing Pearson's correlation coefficients of homogeneous (e.g., physical functioning and pain) of both instruments versus heterogeneous domains (e.g., physical and psychological functioning). We assessed known-groups validity by examining the extent to which HRQOL differed by late effects and comorbid conditions and calculated relative validity (RV) defined as contrasting F-statistics of individual domains to the domain with the lowest F-statistic. Superior known-groups validity is observed if a domain of one instrument demonstrates a higher RV than other domains of the instruments.
  
  
  RESULTS
  YASCC data cannot replicate the constructs both instruments intend to measure, suggesting poor construct validity. Correlations of between-homogeneous and between-heterogeneous domains of both instruments were not discernible, suggesting poor convergent/discriminant validity. Both instruments were equally able to differentiate HRQOL between YASCC with and without late effects and comorbid conditions, suggesting similar known-groups validity.
  
  
  CONCLUSIONS
  Neither instrument is superior. Item response theory is suggested to select high-quality items from different instruments to improve HRQOL measure for YASCC.
authors: Department of Health Outcomes and Policy, University of Florida, Gainesville, FL 32610, USA. ichuang@ufl.edu
authors: I-Chan
authors: IC
authors: Huang
authors: Gwendolyn P
authors: GP
authors: Quinn
authors: Kevin
authors: K
authors: Krull
authors: Katie Z
authors: KZ
authors: Eddleton
authors: Devin C
authors: DC
authors: Murphy
authors: Elizabeth A
authors: EA
authors: Shenkman
authors: Patricia D
authors: PD
authors: Shearer
mesh_terms: D000328:Adult; D005163:Factor Analysis, Statistical; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000523:psychology*; D011594:Psychometrics; D011788:Quality of Life; D011795:Surveys and Questionnaires / Q000592:standards*; D017741:Survivors / Q000523:psychology*; D055815:Young Adult