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Extended report
The development of candidate composite disease activity and responder indices for psoriatic arthritis (GRACE project)
  1. Philip S Helliwell1,2,
  2. Oliver FitzGerald3,
  3. Jaap Fransen4,
  4. Dafna D Gladman5,
  5. Gerald G Kreuger6,
  6. Kristina Callis-Duffin6,
  7. Neil McHugh7,
  8. Philip J Mease8,
  9. Vibeke Strand9,
  10. Robin Waxman1,
  11. Valderilio Feijo Azevedo10,
  12. Adriana Beltran Ostos11,
  13. Sueli Carneiro12,
  14. Alberto Cauli13,
  15. Luis R Espinoza14,
  16. John A Flynn15,
  17. Nada Hassan16,
  18. Paul Healy17,
  19. Eduardo Mario Kerzberg18,
  20. Yun Jong Lee19,
  21. Ennio Lubrano20,
  22. Antonio Marchesoni21,
  23. Helena Marzo-Ortega1,
  24. Giovanni Porru22,
  25. Elvia G Moreta23,
  26. Peter Nash24,
  27. Helena Raffayova25,
  28. Roberto Ranza26,
  29. Siba P Raychaudhuri27,
  30. Euthalia Roussou28,
  31. Raphael Scarpa29,
  32. Yeong Wook Song30,
  33. Enrique R Soriano31,
  34. Paul P Tak32,
  35. Ilona Ujfalussy33,
  36. Kurt de Vlam34,
  37. Jessica A Walsh6
  1. 1Academic Unit of Musculoskeletal Medicine, University of Leeds, Leeds, UK
  2. 2Bradford Teaching Hospitals NHS Foundation Trust, UK
  3. 3St Vincent's University Hospital and University College Dublin, Dublin, Ireland
  4. 4Department of Rheumatology, The Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
  5. 5Centre for Prognosis in the Rheumatic Diseases, University of Toronto, Toronto, Canada
  6. 6Department of Dermatology, University of Utah, Salt Lake City, Utah, USA
  7. 7Royal National Hospital for Rheumatic Diseases, Bath, UK
  8. 8Department of Rheumatology, University of Washington, Seattle, Washington, USA
  9. 9Division of Immunology and Rheumatology, Stanford University, Portola Valley, California, USA
  10. 10Department of Rheumatology, Federal University of Paraná, Rebouças – Paraná, Brasil
  11. 11Clinical Rheumatology, Clinical Rheumatology Hospital de la Policia, Bogota, Colombia
  12. 12University Hospital HUCFF of Federal University of Rio de Janeiro, Rio de Janeiro, Brasil
  13. 13Department of Medical Sciences, Policlinico of the University of Cagliari, Cagliari, Italy
  14. 14Section of Rheumatology, LSU Health Sciences Center, New Orleans, Louisiana, USA
  15. 15School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA
  16. 16Rheumatology Department, Southend University Hospital, Westcliff-on-sea, UK
  17. 17Hutt Valley District Health Board, Lower Hutt, New Zealand
  18. 18School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
  19. 19Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul, Korea
  20. 20Department of Health Sciences, University of Molise, Campobasso, Italy
  21. 21Department of Rheumatology, Istituto Ortopedico G. Pini, Milan, Italy
  22. 22Department of Rheumatology, University of Cagliari, Cagliari, Italy
  23. 23St Paul Rheumatology, Eagan, Minnesota, USA
  24. 24Department of Medicine, University of Queensland, Maroochydore, Australia
  25. 25National Institute of Rheumatic Diseases, Piešt'any, Slovakia
  26. 26Rheumatology Unit, Universidade Federal de Uberlândia, Uberlândia, Brasil
  27. 27Division of Rheumatology, Allergy and Clinical Immunology, University of California Davis, Davis, California, USA
  28. 28Department of Rheumatology, Barking Havering and Redbridge University Hospitals NHS Trust, London, UK
  29. 29University Federico II, Naples, Italy
  30. 30Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea
  31. 31Rheumatology Unit, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina
  32. 32Clinical Immunology and Rheumatology, F4-105, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
  33. 33National Health Center, Military Hospital, Budapest, Hungary
  34. 34Department of Rheumatology, University Hospitals Leuven, Leuven, Belgium
  1. Correspondence to Dr Philip S Helliwell, Leeds Institute of Molecular Medicine, Section of Musculoskeletal Disease, University of Leeds, 2nd Floor, Chapel Allerton Hospital, Harehills Lane, Leeds, LS7 4SA, UK; p.helliwell{at}


Objective To develop new composite disease activity indices for psoriatic arthritis (PsA).

Methods Data from routine clinic visits at multiple centres were collected in a systematic manner. Data included all domains identified as important in randomised controlled trials in PsA. Decisions to change treatment were used as surrogates for high disease activity. New indices were developed by multiple linear regression (psoriatic arthritis disease activity score: PASDAS) and empirically, utilising physician-defined cut-offs for disease activity (arithmetic mean of desirability functions: AMDF). These were compared with existing composite measures: Composite Psoriatic arthritis Disease Activity Index (CPDAI), Disease Activity for PSoriatic Arthritis (DAPSA), and Disease Activity Score for rheumatoid arthritis (DAS28).

Results 161/503 (32%) subjects had treatment changes. Although all measures performed well, compared with existing indices, PASDAS was better able to discriminate between high and low disease activity (area under receiver operating curves (ROC)) curve with 95% CI: PASDAS 0.773 (0.723, 0.822); AMDF 0.730 (0.680, 0.780); CPDAI 0.719 (0.668, 0.770); DAPSA 0.710 (0.654, 0.766); DAS28 0.736 (0.680, 0.792). All measures were able to discriminate between disease activity states in patients with oligoarthritis, although area under the receiver operating curves (AUC) were generally smaller. In patients with severe skin disease (psoriasis area and severity index >10) both nonparametric and AUC curve statistics were nonsignificant for all measures.

Conclusions Two new composite measures to assess disease activity in PsA have been developed. Further testing in other datasets, including comparison with existing measures, is required to validate these instruments.

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