title: Visualization of DAS28, SDAI, and CDAI: the magic carpets of rheumatoid arthritis.
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.
authors.affiliation: Department of Rheumatology, Institute of Medicine, University of Debrecen Medical and Health Science Center, Nagyerdei str 98, Debrecen, 4032, Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Futó
authors.forename: Attila
authors.initials: A
authors.lastname: Somogyi
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Szekanecz
mesh_terms: D018501:Antirheumatic Agents / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000188:drug therapy; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000032:analysis; D006801:Humans; D007249:Inflammation; D007596:Joints / Q000473:pathology; D015203:Reproducibility of Results; D012219:Rheumatology / Q000592:standards; D012720:Severity of Illness Index
chemical_list: D018501:Antirheumatic Agents; D002097:C-Reactive Protein