Background: The European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Group is developing computerized adaptive testing (CAT) versions of each scale of the EORTC Quality of Life Questionnaire (EORTC QLQ-C30). This study aims to develop an item bank for the EORTC QLQ-C30 cognitive functioning scale, which can be used for CAT.

Methods: The complete developmental approach comprised four phases: (I) conceptualization and literature search, (II) operationalization, (III) pretesting, and (IV) field-testing. This paper describes phases I-III.I) A literature search was performed to identify self-report instruments and items measuring cognitive complaints on concentration and memory. II) A multistep item-selection procedure was applied to select and generate items that were relevant and compatible with the 'QLQ-C30 item style.' III) Cancer patients from different countries evaluated the item list for wording (ie, whether items were difficult, confusing, annoying, upsetting or intrusive), and whether relevant issues were missing.

Results: A list of 439 items was generated by the literature search. In the multistep item-selection procedure, these items were evaluated for relevance, redundancy, clarity, and response format, resulting in an list of 45 items. A total of 32 patients evaluated this item list in the pretesting phase, resulting in a preliminary list of 44 items.

Conclusion: Phase I-III resulted in an item list of 44 items measuring self-reported cognitive complaints that was endorsed by international experts and cancer patients in several countries. This list will be evaluated for its psychometric characteristics in phase IV.