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.
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 language | English |
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Pages (from-to) | 79-88 |
Number of pages | 10 |
Journal | Journal of Clinical Epidemiology |
Volume | 69 |
Early online date | 29 Aug 2015 |
DOIs | |
Publication status | Published - Jan 2016 |
Bibliographical note
The authors would like to express their gratitude to many individuals who provided the data used in these analyses, and to Chad Gundy (deceased) who played a key role in the design and execution of the original study investigating the higher order scale structure of the QLQ-C30.Funding: The work of J.M.G. was supported by a grant from the Austrian Science Fund (FWF J3353).
Keywords
- health-related quality of life
- questionnaires
- EORTC QLQ-C30
- measurement model
- higher order factor scores
- confirmatory factor analysis
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Neil Scott
- School of Medicine, Medical Sciences & Nutrition, Applied Health Sciences - Research Fellow
- School of Medicine, Medical Sciences & Nutrition, Medical Statistics
- Institute of Applied Health Sciences
Person: Academic Related - Research