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Extended report
Development of a preliminary composite disease activity index in psoriatic arthritis
  1. Aizad Mumtaz1,
  2. Phil Gallagher1,
  3. Brian Kirby2,
  4. Robin Waxman3,
  5. Laura C Coates3,
  6. Douglas Veale J1,
  7. Philip Helliwell3,
  8. Oliver FitzGerald1
  1. 1Department of Rheumatology, St Vincent's University Hospital, University College Dublin, Dublin, Ireland
  2. 2Department of Dermatology, St Vincent's University Hospital, Dublin, Dublin, Ireland
  3. 3Leeds Institute of Molecular Medicine, Section of Musculoskeletal Disease, University of Leeds, Leeds, UK
  1. Correspondence to Professor Oliver FitzGerald, Bone and Joint Unit, Dublin Academic Health Care, St Vincent's University Hospital, Elm Park, Dublin 4, Ireland; oliver.fitzgerald{at}


Objectives To develop a preliminary composite psoriatic disease activity index (CPDAI) for psoriasis and psoriatic arthritis.

Methods Five domains were assessed and specific instruments were employed for each domain to determine the extent of domain involvement and the effect of that involvement on quality of life/function. Disease activity for each domain was then graded from 0 to 3 giving a CPDAI range of 0–15. Patient and physician global disease activity measures were also recorded and an independent physician was asked to indicate if treatment change was required. Bivariate correlation analysis was performed. Factor, tree analysis and standardised response means were also calculated.

Results Significant correlation was seen between CPDAI and both patient (r=0.834) and physician (r=0.825) global disease activity assessments (p=0.01). Tree analysis revealed that 96.3% of patients had their treatment changed when CPDAI values were greater than 6; no patient had their treatment changed when CPDAI values were less than 5.

Conclusion CPDAI correlates well with patient and physician global disease activity assessments and is an effective tool that clearly distinguishes those who require a treatment change from those who do not.

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  • Funding AM's University College Dublin Newman Fellowship was supported by an unrestricted educational grant from Abbott (Ireland) Ltd. LCC is supported by the Arthritis Research Campaign as an ARC Clinical Research Fellow.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the ethics committees of St Vincents University Hospital Dublin and the University of Leeds.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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