Abstract
There has been continuous debate regarding the applicability of various composite measures for the assessment of disease activity in rheumatoid arthritis (RA). In order to further dissect this issue, we numerically and graphically modeled 28-joint disease activity scale (DAS28), simplified disease activity index (SDAI), and clinical disease activity index (CDAI) by three-dimensional (3D) plotting. We wished to graphically visualize the relative contribution of various elements in the three activity indices to each other. We calculated DAS28 (3 variables), SDAI, and CDAI by the standard equations. We plotted 3D “carpets” showing all combinations of the corresponding variables yielding to DAS28 = 5.1, DAS28 = 3.2, DAS28 = 2.6, SDAI = 26, SDAI = 11, and SDAI = 3.3. We also plotted the 3D carpet for CDAI. In patients with high or moderate disease activity, erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) was not a major confounding factor when calculating DAS28 and SDAI, respectively. In contrast, ESR and CRP highly overshadowed changes in joint counts and global assessments in patients with low disease activity (LDA) or those in remission. No reliable assessment of LDA can be performed in cases where ESR >54 mm/h or CRP >20 mg/dl. Similarly, remission cannot be determined if ESR >19 mm/h or CRP >5 mg/dl. As CDAI does not include acute phase reactants, CDAI may be a useful tool even in states of remission or LDA. Our results suggest that acute phase reactants are indeed major confounding factors and should be omitted when assessing RA disease activity at least in special cases.
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Acknowledgments
This work was supported by research grants ETT 315/2009 from the Medical Research Council of Hungary (Z.S.), OTKA K 105073 from the National Scientific Research Fund of Hungary (Z.S.), WS1695414 and WS1695450 by Pfizer (Z.S.), and by the TÁMOP 4.2.1/B-09/1/KONV-2010-0007 and 4.2.2.A-1/11/KONV-2012-0031 projects co-financed by the European Union and the European Social Fund (Z.S.), by the European Union and the State of Hungary co-financed by the European Social Fund in the framework of TÁMOP-4.2.4.A/2-11/1-2012-0001 ‘National Excellence Program’ (Z.S.), and the University of Debrecen Medical and Health Sciences Center Bridging Fund (Z.S.).
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Futó, G., Somogyi, A. & Szekanecz, Z. Visualization of DAS28, SDAI, and CDAI: the magic carpets of rheumatoid arthritis. Clin Rheumatol 33, 623–629 (2014). https://doi.org/10.1007/s10067-014-2559-5
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DOI: https://doi.org/10.1007/s10067-014-2559-5