The Gout Assessment Questionnaire 2.0: cross-cultural translation into Dutch, aspects of validity and linking to the International Classification of Functioning, Disability and Health

Methods. Recommendations for translation and cross-cultural adaptation were followed and no cultural adaptations were needed. The resulting Dutch GAQ2.0 was administered to patients registered at the rheumatology outpatient clinic diagnosed with gout. Internal consistency was tested using Cronbach's alpha, reliability using intraclass correlation coefficient (ICC), content validity by linkage to the International Classification of Functioning, Disability and Health (ICF) and construct validity by correlating the subscales of the GAQ2.0 with the HAQ disability index (HAQ-DI) and 36-item Short Form Health Survey (SF-36). Results. A total of 126 patients [106 (84%) male, mean age 66.6 years (s.d. 10.4), mean disease duration 11.2 years (s.d. 10.6)] completed a number of questionnaires, including the GAQ2.0, HAQ-DI and SF-36, and underwent a clinical examination. Internal consistency was sufficient (Cronbach's alpha = 0.83-0.94), except for the subscale gout medication side effects (Cronbach's alpha = 0.51). Test-retest reliability was good (ICCs 0.73-0.86) for all subscales, but moderate for the subscale unmet gout treatment need (ICC 0.56). Gout impact (GI) subscale scores showed only weak to moderate correlations with HAQ-DI and SF-36, but stronger emphasis on the emotional consequences of gout. Also, it correlated better with gout-specific outcomes such as the number of gout flares and pain. Conclusion. The Dutch GAQ2.0 shows sufficient evidence of validity to assess disease-specific functioning and health in patients with gout and seems to capture different aspects than those represented in the HAQ and SF-36

Content and construct validity of the Rheumatic Diseases Comorbidity Index in patients with gout

Objective. Gout has been associated with a large number of co-morbidities. As yet, no co-morbidity measure has been validated for use in clinical studies in gout. This study aims to evaluate the content and construct validity of the Rheumatic Diseases Comorbidity Index (RDCI) and a gout-specifically modified RDCI (mRDCI) in patients with gout. Methods. In a cross-sectional sample of 122 patients with gout, data on co-morbidities were obtained during an interview, chart review and clinical examination. The data were used to compute the RDCI/mRDCI, a simple co-morbidity count, the Charlson Comorbidity Index (CCI) and the Functional Comorbidity Index (FCI). Content and construct validity was explored by assessing Spearman correlations between the two RDCI versions and between RDCI/mRDCI and the other co-morbidity indices, as well as demographic and clinical outcomes. In addition, we assessed the independent association between the RDCI/mRDCI and physical functioning (HAQ disability index), physical health (36-Item Short Form Health Survey) and direct health care and non-health care costs using multivariable regression analyses. Results. The correlation between the RDCI and mRDCI was 0.86. Correlations between the RDCI/mRDCI and simple co-morbidity count, CCI or FCI varied between 0.72 and 0.88. Correlations with generic and gout-specific health outcomes were moderate and weak, respectively, with slightly better results for the mRDCI. Multivariable analyses showed that both the RDCI and mRDCI contributed to the variation in physical functioning, physical health and direct health care and non-health care costs. Conclusion. Both the RDCI and mRDCI have appropriate content and construct validity to evaluate the influence of co-morbidity on outcome in patients with gout

Risk of infections in patients with gout: a population-based cohort study

Contains fulltext : 174658.pdf (publisher's version ) (Open Access)To investigate the risk of various types of infections (pneumonia and urinary tract infection (UTI)), and infection-related mortality in patients with gout compared with population-based controls. A retrospective cohort study was conducted using data from the UK Clinical Practice Research Datalink (CPRD). All patients with a first diagnosis of gout and aged >40 years between January 1987-July 2014, were included and matched with up to two controls. Time-varying Cox proportional hazards models were used to estimate the risk of infections and mortality. 131,565 patients and 252,763 controls (mean age: 64 years, 74% males, mean follow-up of 6.7 years) were included in the full cohort. After full statistical adjustment, the risk of pneumonia was increased (adj. HR 1.27, 95% CI 1.18 to 1.36), while the risk of UTI (adj. HR 0.99, 95% CI 0.97 to 1.01) was similar in patients compared to controls. No differences between patients and controls were observed for infection-related mortality due to pneumonia (adj. HR 1.03, 95% CI 0.93 to 1.14) or UTI (adj. HR 1.16, 95% CI 0.98 to 1.37). In conclusion, patients with gout did not have decreased risks of pneumonia, UTI or infection-related mortality compared to population-based controls