Abstract
Objective
To evaluate the reliability and validity of an instrument assessing the influence of gout (acute and chronic) on health-related quality of life (HRQOL).
Methods
Focus groups were used to examine the content of an existing Gout Assessment Questionnaire (GAQ1.0). GAQ2.0 was developed, consisting of a section describing the impact of gout on HRQOL [Gout Impact (GI)] and 4 sections describing subjects’ gout overall and demographic data. The GAQ2.0 and the Medical Outcomes Study Short Form-36 Version 2 (SF-36v2) were completed by gout patients in 3 US cities. GI scales were examined using clinical judgment, review of item statistics, Rasch analysis, and confirmatory factor analysis.
Results
Subjects (n = 308) were predominantly male (90.2%), Caucasian (75.9%), with a mean age 62.2 ± 11.8 years. Half the subjects (49.7%) reported ≥ 3 attacks in the past year. Two-week test-retest reliability for each scale was good (0.77 to 0.89) for all 5 GI scales. All scales achieved high sufficient (0.86 to 0.89) or excellent (0.93 to 0.97) ratings based on 10-item adjusted alpha coefficients. Correlations and tests among known groups indicated subjects with more severe gout had higher GI scores (i.e., greater gout impact). GI scores correlated more highly with patient-reported measures of gout severity than the SF-36v2 and several traditional measures of gout severity.
Conclusion
The GAQ2.0 is an instrument for measuring the impact of gout on HRQOL. The GI section exhibited acceptable reliability and validity characteristics. Future studies should assess GI responsiveness, minimally important differences, and psychometric properties in other patient populations.
Key Indexing Terms:Footnotes
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J.D. Hirsch, PhD, Assistant Professor of Clinical Pharmacy, Skaggs School of Pharmacy and Pharmaceutical Sciences; S.J. Lee, MD, Assistant Professor of Medicine; A. Kavanaugh, MD, Professor of Medicine, Director, Center for Innovative Therapy, Division of Rheumatology, Allergy, and Immunology, University of California, San Diego; R. Terkeltaub, MD, Section Chief, Rheumatology-Allergy, VA San Diego Healthcare Systems; D. Khanna, MD, Assistant Professor of Medicine/Rheumatology, David Geffen School of Medicine, University of California, Los Angeles; J. Singh, MD, Assistant Professor of Medicine/Rheumatology, Minneapolis VA Healthcare; A. Sarkin, PhD, Program Manager; J. Harvey, MA, Project Manager, Health Services Research, University of California, San Diego.
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Supported in part by TAP Pharmaceutical Products, Inc., the GCRC Program (M01 RR00827), National Center for Research Resources, National Institutes of Health, and the VA Research Service.
- Accepted for publication July 3, 2008.
