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

Johannes M. Giesinger, Jacobien M. Kieffer, Peter Fayers, Mogens Groenvold, Morten Aa. Petersen, Neil W. Scott, Mirjam A. G. Sprangers, Galina Velikova, Neil K. Aaronson

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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.
Original languageEnglish
Pages (from-to)79-88
Number of pages10
JournalJournal of Clinical Epidemiology
Volume69
Early online date29 Aug 2015
DOIs
Publication statusPublished - Jan 2016

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Keywords

  • health-related quality of life
  • questionnaires
  • EORTC QLQ-C30
  • measurement model
  • higher order factor scores
  • confirmatory factor analysis

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