Development of computerised adaptive testing (CAT) for the EORTC QLQ-C30 dimensions - general approach and initial results for physical functioning

Abstract

Background: Health-related quality of life (HRQOL) questionnaires should ideally be adapted to the individual patient and at the same time scores should be directly comparable across patients. This is achievable using a computerised adaptive test (CAT). Basing the CAT on an existing instrument enables measurement within an established HRQOL framework and allows backward-compatibility with studies using the original instrument. Because of these advantages the EORTC Quality of Life Group (QLG) has initiated a project to develop a CAT version of the widely used EORTC QLQ-C30.

Methods: We present the EORTC QLG's strategy for developing a CAT. For each dimension of the EORTC QLQ-C30 our approach includes literature search and conceptualisation, formulation of new items, expert and patient evaluations, field-testing, and psychometric analyses of the items. The strategy is illustrated with the initial results of the development of CAT for physical functioning (PF).

Results: We identified 975 PF items in the literature. Of these, 407 items were deemed relevant, i.e. measured one of the PF aspects measured by the QLQ-C30. Based on these items we developed 86 new items. Review by the EORTC CAT-project group reduced this to 66 items. Based on expert and patient evaluations several items were revised and the list was further reduced to 51 items.

Conclusions: Based on the findings for PF, we believe that our approach will generate item pools that are relevant and appropriate for cancer patients. These will form the basis for a backward-compatible CAT assessing the HRQOL dimensions of the EORTC QLQ-C30.