title: A comparison of disease burden in rheumatoid arthritis, psoriatic arthritis and axial spondyloarthritis.
abstract: OBJECTIVE
  The main objective of this study was to compare disease burden in rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondyloarthritis (ax-SpA).
  
  
  METHODS
  In this cross-sectional study, all the RA (1093), PsA (365) and ax-SpA (333) patients who visited the out-patient clinic of the Hospital of Southern Norway Trust during the year 2013 were included; the RA patients all had a RA diagnosis verified by the treating rheumatologist, the PsA patients all fulfilled the ClASsification for Psoriatic ARthritis (CASPAR) criteria and the ax-SpA patients all fulfilled the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for ax-SpA. Patient-reported health status, demographic variables, medications, and composite scores of disease activity were assessed. The main analyses were performed using General Linear Models adjusted for age, sex and multiple comparisons. Correlation analyses were performed using Spearman's rho.
  
  
  RESULTS
  The reported pain, joint pain, patient's global assessment and fatigue were similar in PsA and ax-SpA, but significantly lower in RA. The 28-joint Disease Activity Score (DAS28) (0.3±0.1, p = 0.003), Clinical Disease Activity Index (CDAI) (1.0±0.4, p = 0.028) and Routine Assessment of Patient Index Data 3 (RAPID3) (0.4±0.1, p = 0.004) were all significantly higher in PsA vs. RA. RAPID3 showed moderate to high correlation with DAS28 (rho = 0.521, p<0.001) and CDAI (rho = 0.768, p<0.001) in RA and PsA, and with Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) (rho = 0.902, p<0.001) and Bath Ankylosing Spondylitis Functional Index (BASFI) (0.865, p<0.001) in ax-SpA and PsA.
  
  
  CONCLUSIONS
  In conclusion, patient- reported outcome measures were similar in our population of PsA and ax-SpA patients, but significantly lower for the RA patients. Composite disease activity measures were lower in RA than in PsA and ax-SpA, but the magnitude of these differences was small and probably not of clinical significance. Our study indicates that disease burden in RA, PsA and ax-SpA may be more similar than previously demonstrated.
authors: Department of Rheumatology, Hospital of Southern Norway Trust, Kristiansand, Norway.
authors: Brigitte
authors: B
authors: Michelsen
authors: Norwegian University of Science and Technology, Trondheim, Norway.
authors: Ragnhild
authors: R
authors: Fiane
authors: Department of Rheumatology, Hospital of Southern Norway Trust, Kristiansand, Norway; Norwegian University of Science and Technology, Trondheim, Norway.
authors: Andreas P
authors: AP
authors: Diamantopoulos
authors: Department of Rheumatology, Hospital of Southern Norway Trust, Kristiansand, Norway.
authors: Dag Magnar
authors: DM
authors: Soldal
authors: Department of Rheumatology, Hospital of Southern Norway Trust, Kristiansand, Norway.
authors: Inger Johanne W
authors: IJ
authors: Hansen
authors: Jyväskylä Central Hospital, Jyväskylä, Finland.
authors: Tuulikki
authors: T
authors: Sokka
authors: Division of Rheumatology, Allergy, Immunology, University of California San Diego, San Diego, California, United States of America.
authors: Arthur
authors: A
authors: Kavanaugh
authors: Department of Rheumatology, Hospital of Southern Norway Trust, Kristiansand, Norway; Hospital of Southern Norway Trust, Faculty of Health and Sport Sciences, University of Agder, Kristiansand, Norway.
authors: Glenn
authors: G
authors: Haugeberg
mesh_terms: D000328:Adult; D000368:Aged; D018771:Arthralgia / Q000453:epidemiology; D015535:Arthritis, Psoriatic / Q000453:epidemiology / Q000473:pathology*; D001172:Arthritis, Rheumatoid / Q000453:epidemiology / Q000473:pathology*; D017281:Cost of Illness; D003430:Cross-Sectional Studies; D005221:Fatigue / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D025241:Spondylarthritis / Q000453:epidemiology / Q000473:pathology*