Use of item response theory to develop a shortened version of the EORTC QLQ-C30 emotional functioning scale

European Organisation for Research and Treatment of Cancer Quality of Life Group

    Abstract

    BACKGROUND: As part of a larger study whose objective is to develop an abbreviated version of the EORTC QLQ-C30 suitable for research in palliative care, analyses were conducted to determine the feasibility of generating a shorter version of the 4-item emotional functioning (EF) scale that could be scored in the original metric.

    METHODS: We used data from 24 European cancer studies conducted in 10 different languages (n = 8242). Item selection was based on analyses by item response theory (IRT). Based on the IRT results, a simple scoring algorithm was developed to predict the original 4-item EF sum scale score from a reduced number of items.

    RESULTS: Both a 3-item and a 2-item version (item 21 'Did you feel tense?' and item 24 'Did you feel depressed?') predicted the total score with excellent agreement and very little bias. In group comparisons, the 2-item scale led to the same conclusions as those based on the original 4-item scale with little or no loss of measurement efficiency.

    CONCLUSION: Although these results are promising, confirmatory studies are needed based on independent samples. If such additional studies yield comparable results, incorporation of the 2-item EF scale in an abbreviated version of the QLQ-C30 for use in palliative care research settings would be justified. The analyses reported here demonstrate the usefulness of the IRT-based methodology for shortening questionnaire scales.

    OriginalsprogEngelsk
    TidsskriftQuality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation
    Vol/bind13
    Udgave nummer10
    Sider (fra-til)1683-97
    Antal sider15
    ISSN0962-9343
    DOI
    StatusUdgivet - dec. 2004

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