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Introduction

Introduction

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Introduction

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  1. Methods • DHP-18 validation: • Exploratory factor analysis was used to investigate the factor structure of the DHP-18 • Rasch analysis: • Rasch analysis was used to investigate the performance of the DHP-18 and select items for the DHP-12. Rasch assesses the performance of individual items in relation to the underlying trait measured by the dimension level model. • Rasch assesses: • The ordering of item response categories (disordered items are rescored ) • Differential item functioning (DIF) across different background characteristics • The fit of each item to the overall model • The position of each item on the underlying severity (latent) scale (negative values cover the severe end of the scale, zero is the average, positive values cover the mild end of the scale • Rasch was applied to each of the DHP-18 dimensions across two data subsets • DHP-18/DHP-12 comparison: • The correlations between the measures were assessed • Internal consistency for each domain was assessed using Cronbach’s alpha • A separate comparison sample was used for this analysis • Sample: The Diabetes Health Profile (www.diabeteshealthprofile.com) • The DHP-18 (Meadows et al., 2000): • Assesses psychosocial functioning in Type 2 diabetes across three domains: Psychological Distress; Barriers to Activity; Disinhibited Eating (scored on a 0-100 scale) • Is the diabetes-specific outcome measure selected for the UK Department of Health Patient Reported Outcome Measures Pilot for Long Term Conditions in Primary Care. Discussion • The three domain structure of the Diabetes Health Profile was confirmed. • Rasch analysis indicates that the DHP-18 has satisfactory performance overall. This means that the measure provides a valid basis for the development of a new short diabetes specific PROM. • A variety of Rasch analysis criteria have been used to develop a12 item version of the Diabetes Health Profile (DHP-12) that includes four items in each domain. • Initial psychometric analysis demonstrates evidence for the comparability of the DHP-12 and DHP-18, but the internal consistency of the Barriers to Activity domain is low. Further analysis will be carried out to investigate the relationship in more detail using different datasets. Introduction Results • Factor and Rasch analysis (DHP-12 items highlighted in green) • DHP-12 • Four items from each domain have been selected. • Responses to 10 items are disordered so have been rescored (raw score range is 0-26). • One item (depression due to diabetes) displays DIF by gender. This item has been retained as depression in diabetes has been found to be higher in females (Lustman et al, 1988). • DHP-18/DHP-12 comparison: • There is a need to validate existing patient reported outcome measures (PROMS) to provide evidence on their validity. Subsequently, short measures can be developed from validated PROMS to lessen respondent burden. The aim of this study was to: • Validate the three domain conceptual framework of the Diabetes Health Profile (DHP-18) • Apply Rasch analysis to investigate the performance of the DHP-18 and develop a short 12 item version (DHP-12). MEASURING HEALTH RELATED QUALITY OF LIFE IN DIABETES: THE VALIDATION OF THE DIABETES HEALTH PROFILE (DHP-18) AND THE DEVELOPMENT OF A BRIEF MEASURE OF DIABETES RELATED HRQL (DHP-12) Brendan Mulhern1 & Keith Meadows2 1 Health Economics and Decision Science, University of Sheffield; 2 DHP Research and Consultancy Ltd Contact: Brendan Mulhern, Health Economics and Decision Science, University of Sheffield, Regent Court, Sheffield, S1 4DA; e-mail: b.mulhern@sheffield.ac.uk; website: www.shef.ac.uk/heds Reference: Meadows KA, Abrams C, Sandbaek A. (2000) Adaptation of the Diabetes Health Profile (DHP-1) for use with patients with Type 2 Diabetes mellitus: psychometric evaluation and cross-cultural comparison. Diabetic Medicine; 17: 572-580. Lustman PJ, Griffiths IS, Clouse RE et al. (1988). Depression in adults with diabetes: Results of a 5 year follow up study. Diabetes Care; 11(8): 605-612.