Background: European Organization for Research and Treatment quality of life (QOL) questionnaire (QLQ-C30) has been used frequently and many language versions have been developed, including the simplified Chinese version. It is important to study psychometric properties of the simplified Chinese version from the clinical standpoint.
Patients and methods: The simplified Chinese version of the QLQ-C30 was used in a longitudinal study of 600 patients with five types of cancer: lung, breast, head and neck, colorectal, and stomach. The psychometric properties of the scale were evaluated by indicators of validity and reliability coefficients such as Cronbach's alpha and Pearson's correlation coefficient r, standardized response mean (SRM), correlational analysis, t-tests, and structural equation models.
Results: Correlation and structural equation model analyses confirmed good construct validity with root mean square error of approximation 0.054, standardized root mean square residual 0.037, non-normed fit index 0.972, and comparative fit index 0.980. The alpha coefficients for all domains are >0.7 except for cognitive functioning (0.49). The test-retest reliability coefficients for most domains are >0.80 except for appetite loss (0.77) and diarrhea (0.75). The QOL score changes after treatments were of statistical significance with higher or moderate SRM in most domains.
Conclusion: The simplified Chinese version of QLQ-C30 has good validity, reliability, and responsiveness and can be used to measure QOL for Chinese cancer patients.