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Developing a short-form of the Genetic Counselling Outcome Scale

Grant, Peter 2018. Developing a short-form of the Genetic Counselling Outcome Scale. MPhil Thesis, Cardiff University.
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The aim of this study was to develop a short form of the 24-item Genetic Counselling Outcome Scale (GCOS-24), suitable for use in the clinical setting and in evaluations of genetic counselling and testing services. The study comprised four phases. Phase I: Cognitive interviews were used to explore interpretability of GCOS-24 items and which GCOS-24 items were most valued by the target population. Ten cognitive interviews were conducted with individuals affected by or at risk for a genetic condition, recruited from patient support groups. Phase II: Quantitative analysis of an existing data set of GCOS-24 responses (n = 395), using Classical Test Theory (CTT) methods to identify underlying traits, and Item Response Theory (IRT) methods to examine item discrimination. Phase III: Item Selection. The results from Phases I & II were used to inform the selection of a set of GCOS-24 items. The Rasch rating scale model (Andrich, 1978) was also used to explore functional problems with the seven-point Likert Scale. A six-item questionnaire with a five-point Likert Scale was produced (GCOS-6). In Phase IV the reliability and discriminative ability of the new instrument was tested through a test-retest study. GCOS-6 displays excellent test-retest reliability (0.788) and moderate internal consistency (α = .570). This study represents a potential first step in the development of a measure which could be used in the evaluation of technologies and services used in genetic counselling and testing services.

Item Type: Thesis (MPhil)
Date Type: Completion
Status: Unpublished
Schools: Medicine
Date of First Compliant Deposit: 24 April 2019
Last Modified: 24 Apr 2019 09:48

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