Replication and validation of higher order models demonstrated that a summary score for the EORTC QLQ-C30 is robust

J Clin Epidemiol. 2016 Jan:69:79-88. doi: 10.1016/j.jclinepi.2015.08.007. Epub 2015 Sep 28.

Abstract

Objective: To further evaluate the higher order measurement structure of the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire Core 30 (QLQ-C30), with the aim of generating a summary score.

Study design and setting: Using pretreatment QLQ-C30 data (N = 3,282), we conducted confirmatory factor analyses to test seven previously evaluated higher order models. We compared the summary score(s) derived from the best performing higher order model with the original QLQ-C30 scale scores, using tumor stage, performance status, and change over time (N = 244) as grouping variables.

Results: Although all models showed acceptable fit, we continued in the interest of parsimony with known-groups validity and responsiveness analyses using a summary score derived from the single higher order factor model. The validity and responsiveness of this QLQ-C30 summary score was equal to, and in many cases superior to the original, underlying QLQ-C30 scale scores.

Conclusion: Our results provide empirical support for a measurement model for the QLQ-C30 yielding a single summary score. The availability of this summary score can avoid problems with potential type I errors that arise because of multiple testing when making comparisons based on the 15 outcomes generated by this questionnaire and may reduce sample size requirements for health-related quality of life studies using the QLQ-C30 questionnaire when an overall summary score is a relevant primary outcome.

Keywords: Confirmatory factor analysis; EORTC QLQ-C30; Health-related quality of life; Higher order factor scores; Measurement model; Questionnaires.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Female
  • Humans
  • Male
  • Middle Aged
  • Models, Statistical*
  • Neoplasms* / therapy
  • Quality of Life*
  • Surveys and Questionnaires*