title: Responsiveness of a simple RAPID-3-like index compared to disease-specific BASDAI and ASDAS indices in patients with axial spondyloarthritis.
abstract: OBJECTIVE
  To evaluate the responsiveness of a simple routine assessment of patient index data (RAPID3)-like index that includes only 3 patient self-report measures (physical function, pain and patient global estimate) compared to that of traditional composite indices to assess change in patients with axial spondyloarthritis (Ax-SpA).
  
  
  METHODS
  Devenir des Spondylarthropathies Indifférenciées Récentes (DESIR) is a prospective cohort of patients with inflammatory back pain suggestive of Ax-SpA. The study included 461 patients, who met the Assessment of SpondyloArthritis International Society (ASAS) classification criteria for Ax-SpA. A simple RAPID3-like index was compared with the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the AS Disease Activity Score (ASDAS) scores for responsiveness over 6 months. Construct validity was also evaluated through Pearson correlations and discrimination of disease activity through standardised mean differences for the 3 indices.
  
  
  RESULTS
  The RAPID3-like index was correlated significantly with BASDAI (r=0.84, p<0.005) and ASDAS-C-reactive protein (CRP) (r=0.74, p<0.005), similar to correlations of BASDAI with ASDAS-CRP (r=0.76, p<0.005). The percentage of patients with inactive disease ranged from 9% to 25% and with high activity from 10% to 45%, according to various measures. The capacity to discriminate between high and low disease activity was similar for the 3 indices. The strength of agreement of RAPID3 with ASDAS-CRP was moderate (0.44) and lower with BASDAI (0.37). Responsiveness over 6 months was slightly higher for ASDAS-CRP and the RAPID3-like index than that for BASDAI.
  
  
  CONCLUSIONS
  The RAPID3-like index provides similar information to BASDAI and ASDAS-CRP concerning responsiveness over 6 months. RAPID3 appears feasible to assess patients with Ax-SpA quantitatively over time in busy clinical settings.
authors.affiliation: Rush University Medical Center , Chicago, Illinois , USA.
authors.forename: Isabel
authors.initials: I
authors.lastname: Castrejón
authors.affiliation: Rush University Medical Center , Chicago, Illinois , USA.
authors.forename: Theodore
authors.initials: T
authors.lastname: Pincus
authors.affiliation: CHRU de Besançon, Université de Franche-Comté , Besançon , France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Wendling
authors.affiliation: Department of Rheumatology-Hôpital Cochin , Paris Descartes University, Assistance Publique-Hôpitaux de Paris INSERM (U1153): Clinical Epidemiology and Biostatistics, PRES Sorbonne Paris-Cité , Paris , France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Dougados
keywords: Disease Activity; Outcomes research; Patient perspective; Spondyloarthritis