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Arthritis Care Res (Hoboken). 2016 Oct;68(10):1530-7. doi: 10.1002/acr.22844. Epub 2016 Sep 6.

Development and First Validation of a Disease Activity Score for Gout.

Author information

1
Italian Society for Rheumatology, Milan, Italy. c.scire@reumatologia.it.
2
Italian Society for Rheumatology, Milan, Italy.
3
University of Bologna, Bologna, Italy.
4
University of Genoa, Genoa, Italy.
5
University of Otago, Wellington, New Zealand.
6
University of Ferrara, Ferrara, Italy.
7
Polytechnic University of Marche, Ancona, Italy.
8
University of Padua, Padua, Italy.
9
IRCCS San Matteo Foundation, Pavia, Italy.
10
University of Florence, Florence, Italy.
11
San Camillo Hospital, Rome, Italy.

Abstract

OBJECTIVE:

To develop a new composite disease activity score for gout and provide its first validation.

METHODS:

Disease activity has been defined as the ongoing presence of urate deposits that lead to acute arthritis and joint damage. Every measure for each Outcome Measures in Rheumatology core domain was considered. A 3-step approach (factor analysis, linear discriminant analysis, and linear regression) was applied to derive the Gout Activity Score (GAS). Decision to change treatment or 6-month flare count were used as the surrogate criteria of high disease activity. Baseline and 12-month followup data of 446 patients included in the Kick-Off of the Italian Network for Gout cohort were used. Construct- and criterion-related validity were tested. External validation on an independent sample is reported.

RESULTS:

Factor analysis identified 5 factors: patient-reported outcomes, joint examination, flares, tophi, and serum uric acid (sUA). Discriminant function analysis resulted in a correct classification of 79%. Linear regression analysis identified a first candidate GAS including 12-month flare count, sUA, visual analog scale (VAS) of pain, VAS global activity assessment, swollen and tender joint counts, and a cumulative measure of tophi. Alternative scores were also developed. The developed GAS demonstrated a good correlation with functional disability (criterion validity) and discrimination between patient- and physician-reported measures of active disease (construct validity). The results were reproduced in the external sample.

CONCLUSION:

This study developed and validated a composite measure of disease activity in gout. Further testing is required to confirm its generalizability, responsiveness, and usefulness in assisting with clinical decisions.

PMID:
26815286
PMCID:
PMC5129490
DOI:
10.1002/acr.22844
[Indexed for MEDLINE]
Free PMC Article

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