Development of computerized adaptive testing (CAT) for the EORTC QLQ-C30 physical functioning dimension



Computerized adaptive test (CAT) methods, based on item response theory (IRT), enable a patient-reported outcome instrument to be adapted to the individual patient while maintaining direct comparability of scores. The EORTC Quality of Life Group is developing a CAT version of the widely used EORTC QLQ-C30. We present the development and psychometric validation of the item pool for the first of the scales, physical functioning (PF).


Initial developments (including literature search and patient and expert evaluations) resulted in 56 candidate items. Responses to these items were collected from 1,176 patients with cancer from Denmark, France, Germany, Italy, Taiwan, and the United Kingdom. The items were evaluated with regard to psychometric properties.


Evaluations showed that 31 of the items could be included in a unidimensional IRT model with acceptable fit and good content coverage, although the pool may lack items at the upper extreme (good PF). There were several findings of significant differential item functioning (DIF). However, the DIF findings appeared to have little impact on the PF estimation.


We have established an item pool for CAT measurement of PF and believe that this CAT instrument will clearly improve the EORTC measurement of PF.

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The study was funded by grants from the EORTC Quality of Life Group. National Taiwan University, grant National Science Council, Taiwan, No. 95-2314-B-002-266-MY2, 97-2314-B-002-020-MY3.

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Correspondence to Morten Aa. Petersen.

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This study is conducted on behalf of the EORTC Quality of Life Group.

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Petersen, M.A., Groenvold, M., Aaronson, N.K. et al. Development of computerized adaptive testing (CAT) for the EORTC QLQ-C30 physical functioning dimension. Qual Life Res 20, 479–490 (2011).

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  • Computerized adaptive test
  • Item banking
  • Item response theory
  • Physical functioning
  • Quality of life