The project introduces a new approach to standardizing disease-specific assessments of Health-Related Quality of Life (HRQOL) to achieve the advantages of both generic questionnaires, which can be compared across which have greater sensitivity and specificity. The approach builds on: (1) an item bank representing the most frequently measured domains of disease impact (e.g., role functioning, social functioning, and psychological distress), standardized across diseases, and (2) instructions to assess the impact of a specific disease (e.g., arthritis, diabetes) in answering each questionnaire item. The approach uses item response theory (IRT) and computerized adaptive testing (CAT) software to yield more practical and precise assessments over a wide range of disease conditions and severity levels - eliminating """"""""ceiling"""""""" and """"""""floor"""""""" effects. CAT software will be programmed to select and administer the most informative and relevant disease impact questions for each patient, with consideration of the clinical application. Standardization of the content of disease-specific impact items and calibration of these items across diseases makes it possible to achieve more responsive outcomes measures, while enabling meaningful comparisons across diseases/-treatments. Previous work has used IRT methodology to develop a bank of items with equivalent item calibrations across five diseases.
The aims of Phase I of this project are to analyze existing data sets to evaluate the equivalence of these item calibrations across age groups and to test the feasibility of the Disease Impact CAT approach for elderly patients in a clinical setting. The feasibility study will use a prototype Disease Impact CAT to collect new data from 100 middle aged and elderly patients within five groups: arthritis, depression, chronic obstructive pulmonary disease, diabetes, and osteoporosis. Separate feedback reports will be developed for the patients and the clinicians. Feasibility will be evaluated in terms of respondent burden, range of levels measured, item usage, and response consistency, as well as the clinicians' and patients' experience using the prototype CAT tool and the feedback reports. The product of Phase I will be a prototype Disease Impact CAT with preliminary evidence regarding feasibility and acceptance. Phase II will develop and further evaluate the potential of a comprehensive Disease Impact CAT Assessment System, standardized across primary and comorbid chronic diseases/conditions, in terms of psychometric performance and usefulness in clinical research and practice.
