Description and prediction of physical functional disability in psoriatic arthritis: a longitudinal analysis using a Markov model approach

Arthritis Rheum. 2005 Jun 15;53(3):404-9. doi: 10.1002/art.21177.


Objective: To describe the longitudinal course of physical functioning in patients with psoriatic arthritis.

Methods: Between June 1993 and June 2003, 341 patients attending the University of Toronto Psoriatic Arthritis Clinic completed 2 or more Health Assessment Questionnaires (HAQs). At the time of administration of each HAQ, patients were assigned to 1 of 3 physical functional disability states, based on their HAQ score. A Markov model that allowed for transitions to and from these 3 disability states was used to characterize the longitudinal course of physical functioning, as well as to identify factors for both progression and regression of disability.

Results: Despite patient variability in the course of physical functioning, the following 3 longitudinal patterns were observed: 1) a stable state of disability throughout the entire study period, with 28%, 12%, and 6% of patients experiencing no, moderate, or severe disability, respectively; 2) a steady improvement or deterioration in disability over time (this pattern was observed in 27% of patients); and 3) a fluctuating state of disability, occurring in 27% of the patients. Sex, age, disease duration, number of actively inflamed joints, and number of deformed joints predicted transitions between disability states.

Conclusion: Although 28% of patients appeared resistant to becoming disabled over the duration of this study, the remaining patients were observed either to experience enduring disability or to move between disability states.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arthritis, Psoriatic / physiopathology*
  • Disability Evaluation
  • Disease Progression
  • Female
  • Humans
  • Longitudinal Studies
  • Male
  • Markov Chains*
  • Middle Aged
  • Surveys and Questionnaires