Assessing the reliability of the EORTC QLQ-C30 in a sample of older African American and Caucasian adults.

The purpose of this study was to examine the structure and reliability of the EORTC QLQ-C30. This 30-item instrument has five functional scales (physical, role, cognitive, emotional, and social), three symptom scales (fatigue, pain, and nausea and vomiting) and a global health and quality of life scale. Confirmatory factor analysis and Cronbach's alpha estimates were used to assess the functioning of the EORTC QLQ-C30 in a sample of 489 African American (n = 255) and Caucasian (n = 234) adults aged 50 + years. Seven of the nine EORTC QLQ-C30 scales showed good reliability for both the African Americans and the Caucasians in the sample (Cronbach's alpha > 0.75). In contrast, the cognitive functioning scale had a reliability coefficient of only 0.69 for the African Americans and 0.40 for the Caucasians, and the nausea and vomiting scale had a reliability coefficient of only 0.49 for the African Americans and 0.51 for the Caucasians. In summary, although the overall reliabilities of seven of the scales showed good fit, many of the item-to-scale correlations did not. Researchers planning to use the EORTC QLQ-C30 might first consider conducting separate analyses on the different racial or ethnic subgroups in their study populations to determine whether a common set of factors or scales is available for further analysis.