EORTC QLQ-CAT: Validation of the EORTC computerized adaptive testing (CAT) instrument

The EORTC QLQ-C30 questionnaire was developed by the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Group. This questionnaire is frequently used in studies investigating the health-related quality of life of cancer patients. The third version of the questionnaire comprises 30 items, which are grouped into 15 domains of health-related quality of life. This questionnaire is a traditional paper-and-pencil questionnaire, i.e. the questions should be completed by all patients in the same order. This ensures direct comparability of results. However, this also carries the risk that some patients will receive several questions on domains by which they are not affected. Ideally, the questionnaire should be adapted to individual patients without compromising cross-cultural and interindividual comparability. CAT systems based on item response theory (IRT) take this into account. In this study, an IRT-based CAT will be developed (development phase) and validated (validation phase).