Yorke, J 'A critique of Rasch analysis for the development of patient-centred outcomes: an illustrative example using the Dyspnoea-12' , Journal Of Advanced Nursing . (Submitted)

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Abstract

Background: The development of questionnaires has traditionally involved the application of classical test theory (CTT). More recently Rasch analysis has gained momentum as a robust application of ‘modern’ psychometric testing for the development of new instruments and the refinement of existing ones. Aim: This paper is a report of the application of Rasch analysis to the development and refinement of the Dyspnoea-12 questionnaire; an instrument that measures breathlessness severity using descriptor items. The aim is to provide a critique and working example of Rasch analysis techniques. Method: 358 patients with a cardiopulmonary disease responded to an initial list of 81 items. Hierarchical modeling reduced the list to 34 items. Subsequent Rasch analysis was used to informed decisions regarding further item removal and fit to the unidimensional model. This paper presents the application of Rasch analysis to these 34 items. Results: 22 items failed to reach the requirements of the Rasch model and were removed. Conclusion: This paper provides a working example of Rasch analysis. We have presented the steps involved in reducing and refining a large item-set by identifying those items which possessed the most reliable measurement properties. We have provided nurse researchers with an alternative to CTT when developing or refining questionnaires that measure patient-centred outcomes.

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