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Patient Centered Assessment of Ankylosing Spondylitis-Specific Health Related Quality of Life: Evaluation of the Patient Generated Index
KIRSTIE L. HAYWOOD, ANDREW M. GARRATT, KRYSIA DZIEDZIC, and PETER T. DAWES
ABSTRACT.
Methods. The PGI asks patients to nominate areas of their lives affected by their disease that they consider the most important. Semistructured interviews with AS patients produced a trigger list of areas of life affected by AS. The PGI was self-completed by UK patients taking part in a multicenter postal survey. The instrument was assessed for data quality, reliability, validity, and responsiveness. Results. The PGI had acceptable completion rates. Scores covered the available range and approximated normality. Test-retest reliability estimates support the use of the PGI in group evaluation (intraclass correlation coefficient > 0.80). Comparisons with scores for other health status instruments provided evidence for the validity of the PGI. The largest levels of correlation were found for the AS Quality of Life Questionnaire (ASQoL) and the EuroQol. The informed and open format of the PGI had the strongest linear relationship with responses to both specific and general health transition questions (p < 0.01), and was the most responsive format of the PGI. Conclusion. The PGI is the first AS-specific individualized measure of health related quality of life. There is good support for the content validity of the instrument and patient acceptability is high. Adequate levels of data quality and reliability support the use of the PGI in group evaluation. Moderate levels of responsiveness to changes in health were produced by the informed and open format of the PGI. (J Rheumatol 2003;30:764-73) Key Indexing Terms:
ANKYLOSING SPONDYLITIS
From the Interdisciplinary Research Centre in Health, Physiotherapy and Dietetics Subject Group, School of Health and Social Sciences, Coventry University, Coventry; the Unit of Health-Care Epidemiology, Department of Public Health, University of Oxford, Oxford; Department of Physiotherapy Studies and Primary Care Sciences Research Centre, Keele University, Keele; and Staffordshire Rheumatology Centre, Stoke-on-Trent, England. Supported by a grant from the Arthritis Research Campaign and the Staffordshire Rheumatology Centre. K.L. Haywood, PhD, DPhil, Research Fellow, Senior Lecturer in Physiotherapy (Research Methods), University of York; A.M. Garratt, PhD, Research Officer, University of Aberdeen, Scotland; K. Dziedzic, PhD, Arthritis Research Campaign Senior Lecturer in Physiotherapy, Keele University; P.T. Dawes, MB, ChB, FRCP(UK), Consultant Rheumatologist. Address reprint requests to Dr. A.M. Garratt, Unit of Health-Care Epidemiology, Institute of Health Sciences, Old Road, Oxford OX3 7LF, UK. E-mail: andrew.garratt@uhce.ox.ac.uk Submitted January 28, 2002; revision accepted October 28, 2002. |