Assessing measurement invariance in the EORTC QLQ-C30.

Area of Science:

• Psychometrics
• Cancer Research
• Health Outcomes

Background:

• The European Organisation for research and treatment of cancer quality of life questionnaire core 30 (EORTC QLQ-C30) is widely used to assess cancer patient quality of life.
• Ensuring measurement invariance (MI) is crucial for valid cross-group comparisons of quality of life (QoL) data.

Purpose of the Study:

• To investigate the measurement invariance (MI) of the EORTC QLQ-C30 in a heterogeneous sample of cancer patients.
• To assess the validity of using the EORTC QLQ-C30 across diverse patient subgroups.

Main Methods:

• Secondary analysis of data from 7007 patients across 12 studies in the PROFILES registry.
• Multigroup confirmatory factor analysis (MGCFA) was used to test MI across subgroups (cancer site, age, sex, time since diagnosis, life stage).
• Impact of parameter equality on latent factor means was evaluated by releasing constraints.

Main Results:

• The EORTC QLQ-C30 demonstrated the highest MI across groups based on time since diagnosis and life stage.
• Moderate MI was observed across groups based on sex, age, and primary tumor site.
• Item-level analysis showed minimal impact of non-invariance on latent factor means.

Conclusions:

• Valid conclusions can be drawn from between-group comparisons of EORTC QLQ-C30 latent means.
• Further research on MI in other subgroups (e.g., treatment effects, ethnicity) is recommended.
• MI evaluations are essential for developing and validating measurement instruments.