RT Journal Article
SR Electronic
T1 Comparison of the Construct Validity and Sensitivity to Change of the Visual Analog Scale and a Modified Rating Scale as Measures of Patient Global Assessment in Rheumatoid Arthritis
JF The Journal of Rheumatology
JO J Rheumatol
FD The Journal of Rheumatology
SP jrheum.090764
DO 10.3899/jrheum.090764
A1 Chili Lati
A1 Lori C. Guthrie
A1 Michael M. Ward
YR 2010
UL http://www.jrheum.org/content/early/2010/02/24/jrheum.090764.abstract
AB Objective Patient global assessment (PGA) is commonly measured using a visual analog scale (VAS). The VAS asks patients to integrate many dimensions of rheumatoid arthritis (RA) activity, yet its scope is poorly defined and its endpoints are vague. We investigated whether a modified Rating Scale that used marker states and more defined endpoints would provide a more valid measure of PGA. Methods In our prospective longitudinal study, 164 patients with active RA rated their global arthritis activity using the VAS and Rating Scale before and after treatment. To compare construct validity, we correlated each score with 2 reference measures of RA activity, the 28-joint count Disease Activity Score (DAS28) and the physician global assessment, and examined how each measure was associated with different aspects of RA activity, including pain, functioning, and depressive symptoms, in multivariate regression analyses. We also examined sensitivity to change. Results Both measures were correlated with the DAS28 (r = 0.39 for VAS; r = 0.35 for Rating Scale) and physician global assessment (r = 0.41 for VAS; r = 0.26 for Rating Scale) at the baseline visit. Pain and depressive symptoms had the strongest association with the VAS, while functional limitations and depressive symptoms had the strongest association with the Rating Scale. Residual analysis showed no differences in heterogeneity of patients’ ratings. VAS was more sensitive to change than the Rating Scale (standardized response means of 0.55 and 0.45). Conclusion As measures of PGA, the VAS and Rating Scale had comparable construct validity, but differed in which aspects of arthritis activity influenced scores. VAS was more sensitive to change.