Background Gout is the most prevalent arthritis and significantly impacts on function. Identifying disease-related prognostic factors may help to improve management and prevent disability.
Objectives This study aims to evaluate the association of disease-related factors with functional disability over time and relative importance in patients with gout.
Methods This is prospective analysis of a multicentre cohort study including patients with a clinical diagnosis of gout (KING Study, promoted by SIR, NCT01549210) recruited between June 2011 and January 2012. All patients underwent full clinical evaluation, recording variables belonging to five different domains: socio-demographics, life-styles and comorbidities, treatments, gout-related variables (diagnosis, duration, pattern of disease, tophi burden, joint examination and serum uric acid (sUA) levels). Functional disability was assessed by the health assessment questionnaire (HAQ) at baseline and 12 months. The primary outcome was defined as persistency of or worsening of functional disability at 12 months (according to the following HAQ classes: absent 0–0.5; mild 0.5–1; moderate 1–2; severe 2–3). Logistic models were used to explore the relationship between predictors and outcome. A prognostic model was built selecting variables (backward) within the domains, and combining them thereafter. Discrimination and calibration of the final model was tested by the area under the ROC curve (AUC) and the Hosmer-Lemeshow test. Bootstrap internal validation was performed. Results are presented as odds ratio (OR) and 95% confidence interval (CI).
Results A total of 446 patients were included in the analyses. 90% were men and mean (SD) age was 63.9 (11.6) years. Gout-related factors associated with worse functional outcome after 12 months are reported in Table.
A comprehensive prognostic model for 12-month disability was developed, finally including: baseline HAQ (OR [95% CI]: 7.52 [4.16-13.59]), sUA levels [cut off: 6 mg/dl] (2.13 [1.09-4.16]), index of comorbidity (1.12 [1.02-1.22]) and number of tender joints (1.55 [0.73-3.28] 2-4 vs 0-1; 3.32 [1.42-7.78] >4 vs 0-1). The model showed a good performance (AUC of 0.877), calibration and internal validity.
Conclusions Disease-specific variables independently impact on function over time, suggesting that a stricter control of the disease may improve the excess of disability observed in gout.
Disclosure of Interest None declared