ACR Meeting Abstracts

ACR Meeting Abstracts

Abstract Number: 0796

Validation of the Simplified Disease Activity Index (SDAI) with a Quick Quantitative C-reactive Protein Assay (SDAI-Q) in Patients with Rheumatoid Arthritis: A National, Multicenter Study

Julia Schally1, Henning Christian Brandt2, Jan Brandt-Jrgens3, Gerd Burmester4, Hildrun Haibel5, Henriette Käding1, Kirsten Karberg6, Susanne Lüders7, Burkhard Muche1, Mikhail Protopopov4, Valeria Rios Rodriguez4, Murat Torgutalp4, Maryna Verba8, Silke Zinke9, Denis Poddubnyy10 and Fabian Proft4, 1Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Gastroenterology, Infectiology and Rheumatology (including Nutrition Medicine), Berlin, Germany, 2Praxis für Rheumatologie und Innere Medizin, Berlin, Germany, 3Rheumatologische Schwerpunktpraxis, Berlin, Germany, 4Charité University Medicine Berlin, Berlin, Germany, 5Department of Gastroenterology, Infectiology and Rheumatology (including Nutrition Medicine), Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany, 6Praxis für Rheumatologie und Innere Medizin,, Berlin, Germany, 7Department of Gastroenterology, Infectiology and Rheumatology (including Nutrition Medicine), Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany, Berlin, Germany, 8Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin Department of Gastroenterology, Infectiology and Rheumatology (including Nutrition Medicine), Berlin, Germany, 9Rheumapraxis Berlin, Berlin, Germany, 10Department of Rheumatology, Charité – Universitätsmedizin, Berlin, Germany

Meeting: ACR Convergence 2021

Keywords: , ,

Session Information

Date: Sunday, November 7, 2021

Session Title: RA – Diagnosis, Manifestations, & Outcomes Poster II: Miscellaneous Aspects of RA (0786–0812)

Session Type: Poster Session B

Session Time: 8:30AM-10:30AM

Background/Purpose: Therapeutic decisions in RA patients should be based on regular disease activity assessment using scores like the Simplified Disease Activity Index (SDAI) or the Clinical Disease Activity Index (CDAI) [1]. The CDAI has the benefit of being immediately available, while the SDAI encompasses with the C-reactive protein (CRP) an acute phase reactant and therefore is the recommended score for the use in clinical trials. However, CRP determination takes hours to days, thus hindering the treat-to-target concept using the SDAI. Quick quantitative CRP (qCRP) tests allow CRP measurement within a few minutes. Therefore, qCRP based SDAI (SDAI-Q) could combine the advantages of both scores. The objective of our study was to validate the SDAI-Q in a prospective, multicenter study of RA patients.

Methods: The study was conducted in five centers in Berlin, Germany. Consecutive adult (≥ 18 years) RA patients were included. In addition to a rheumatological assessment, including patient reported outcomes, routine CRP was measured in the local labs. Additionally, a qCRP testing with the „QuikRead go instrument“ (Aidian Oy, Finland) was performed locally (measurement range 0.5 – 200 mg/l). Statistical analysis included descriptive statistics, cross tabulation and weighted Cohen´s kappa comparing disease activity categories, Bland-Altman plots and intraclass correlation coefficient (ICC) for CRP, qCRP, SDAI, SDAI-Q and CDAI.

Results: In this study 100 RA patients were included (mean age: 60.9 years, mean disease duration: 11.4 years, 73.0% were female, 63.0% RF positive, 57.0% ACPA positive, 49.0% positive and 29% negative for both parameters). 75.0% were treated with csDMARD, 15% with tsDMARDs, 39.0% with bDMARDs and 40% with glucocorticoids (mean prednisolone equivalent: 5.4 mg prednisolone/d). Mean CRP and qCRP-levels were 6.97 and 7.89 mg/l, respectively (ICC 0.992; 95%CI: 0.987; 0.995). Comparing SDAI-Q and SDAI, all patients (100%) achieved the same disease activity status (Table 1A); weighted Cohen´s kappa was 1.000 (95%CI: 1.000; 1.000). ICC for SDAI-Q- and SDAI-values was 1.000 (95%CI: 1.000; 1.000). The agreement of SDAI-Q and SDAI is shown in a Bland-Altman plot (Figure 1). When comparing the CDAI with the SDAI-Q 93 patients (93%) were assigned to the same disease activity category (Table 1B); weighted Cohen´s kappa was 0.929 (95%CI: 0.878; 0.981). ICC for numerical values of SDAI-Q and CDAI was 0.989 (95%CI: 0.978; 0.994).

Conclusion: SDAI-Q showed an absolute agreement with SDAI on the assignment to disease activity categories with the important advantage of time. With SDAI-Q, rheumatologists could base their clinical decision-making immediately on an index-based disease activity measurement by using a composite score considering acute phase reactants. Consequently, SDAI-Q can be integrated in clinical routine and clinical trials and could be implemented into the treat-to-target concept in RA patients.

References:
1. Smolen JS, et al. Ann Rheum Dis. 2016 Jan; 75(1):3-15.

Acknowledgements: The authors would like to deeply thank Braun T, Doerwald C, Deter N, Höppner C, Lackinger J, Lorenz C, Lunkwitz K, Mandt B, Sron S and Zernicke J for their practical support and coordinating the study.

Table 1: A) Disease activity categories by SDAI-Q vs. SDAI; B) Disease activity categories by SDAI-Q vs.CDAI

Bland-Altman plot for SDAI and SDAI-Q

Disclosures: J. Schally, None; H. Brandt, None; J. Brandt-Jrgens, Abbvie, 2, 6, Pfizer, 2, 6, Roche, 2, 6, Sanofi-Aventis, 2, 6, Novartis, 2, 6, Eli Lilly, 2, 6, MSD, 2, 6, UCB, 2, 6, BMS, 2, 6, Janssen, 2, 6, Medac, 2, 6; G. Burmester, AbbVie, 2, 5, 6, Eli Lilly, 2, 5, 6, MSD, 2, 5, 6, Pfizer, 2, 5, 6, Roche, 2, 5, 6, Sanofi, 2, 5, 6, UCB, 2, 5, 6, Galapagos, BV, 2, 6, Gilead Sciences, Inc., 2, 6; H. Haibel, Boehringer, 2, Janssen, 2, 6, MSD, 2, 6, Pfizer, 6, Novartis, 2, Roche, 2, 6, AbbVie, 6; H. Käding, None; K. Karberg, AbbVie, 2, 6, Lilly, 2, 6, Roche, 2, 6, Novartis, 2, 6, Sanofi, 2, 6, Galapagos, 2, 6; S. Lüders, None; B. Muche, None; M. Protopopov, Novartis, 1, 5, 6; V. Rios Rodriguez, None; M. Torgutalp, None; M. Verba, None; S. Zinke, None; D. Poddubnyy, AbbVie, 2, 5, 6, Eli Lilly and Company, 2, 5, 6, MSD, 2, 5, 6, Novartis, 2, 5, 6, Pfizer, 2, 5, 6, UCB, 2, 6, BMS, 2, 6, Roche, 2, 6; F. Proft, Novartis, 6.

To cite this abstract in AMA style:

Schally J, Brandt H, Brandt-Jrgens J, Burmester G, Haibel H, Käding H, Karberg K, Lüders S, Muche B, Protopopov M, Rios Rodriguez V, Torgutalp M, Verba M, Zinke S, Poddubnyy D, Proft F. Validation of the Simplified Disease Activity Index (SDAI) with a Quick Quantitative C-reactive Protein Assay (SDAI-Q) in Patients with Rheumatoid Arthritis: A National, Multicenter Study [abstract]. Arthritis Rheumatol. 2021; 73 (suppl 9). https://acrabstracts.org/abstract/validation-of-the-simplified-disease-activity-index-sdai-with-a-quick-quantitative-c-reactive-protein-assay-sdai-q-in-patients-with-rheumatoid-arthritis-a-national-multicenter-study/. Accessed October 1, 2022.

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