To the Editor:
We greatly appreciate the comments from Profs. Pincus and Schmukler.1 We strongly agree that the Routine Assessment of Patient Index Data 3 (RAPID3) is an excellent instrument to provide quantitative data on the status of our patients with axial spondyloarthritis (axSpA), as shown by the studies cited. Our group cross-culturally adapted and validated the RAPID3 in 51 consecutive patients aged ≥ 18 years diagnosed with axSpA (according to modified New York criteria 1987 and/or Assessment of SpondyloArthritis international Society [ASAS] 2009).2-4 RAPID3 has shown to be a questionnaire that is not only quick and simple to calculate and complete but also has very good correlation with Simplified Ankylosing Spondylitis Disease Activity Score (SASDAS; ρ 0.87), Bath Ankylosing Spondylitis Disease Activity Index (ρ 0.89), Bath Ankylosing Spondylitis Functional Index (BASFI; ρ 0.8), and Ankylosing Spondylitis Quality of Life (ASQoL; ρ 0.83), and a good correlation with Maastricht Ankylosing Spondylitis Enthesitis Score (ρ 0.58).4 “In multiple linear regression, using total RAPID3 score as a dependent variable and adjusting for age, sex, and disease duration, a significant association was observed” with BASFI (β 0.25, P = 0.008), ASQoL (β 0.22, P = 0.02), and mainly with SASDAS (β 0.42, P = 0.001) and BASDAI (β 0.55, P = 0.0001).4 In relation to Fibromyalgia Assessment Screening Tool 4 (FAST4), we have no experience with it; however, we believe it is important to include in clinical practice a simple tool that allows health practitioners to identify patients with fibromyalgia since it is a prevalent comorbidity in these patients.
However, the ASDAS has shown excellent performance in the evaluation of patients with axSpA5-7: it is part of the ASAS-Outcome Measures in Rheumatology (OMERACT) core domain set for axSpA8 and has been chosen as a point of reference for treat-to-target strategy in axSpA.9 This composite index includes both subjective variables related to axial involvement and an objective laboratory value such as C-reactive protein, and its cut-off points have excellent power of discrimination and allow definition of the different states of disease activity.
Finally, we consider that the SASDAS has a performance similar to that of the ASDAS but that it is simpler to calculate and does not require the weighting of its components.10,11 However, it is the future task of our group to review the cut-off points of the SASDAS, to further improve its performance. Again, we thank Drs. Pincus and Schmukler, who certainly honor us with their letter.
Footnotes
The authors declare no conflicts of interest relevant to this article.
- Copyright © 2023 by the Journal of Rheumatology
