Clinical and radiological damage in psoriatic arthritis

Background: Psoriatic arthritis may progress to joint damage. Joint damage may be assessed clinically, by identifying deformed, fused, or flail joints, or radiologically, by recording erosions, joint space narrowing, ankylosis, lysis, or surgery. The relation between clinical and radiological damage is unclear. Objective: To study the ordering of clinical and radiological damage detection, and the clinical features associated with the type of damage detected first. Methods: The University of Toronto psoriatic arthritis database was used to relate clinical and radiological damage in the hand joints in 655 patients followed prospectively between 1978 and 2003. Generalised estimating equations were used to fit logistic regression models to identify factors that predict classification of damage by radiographic assessment first. Results: The majority of the joints were not informative, as they either had evidence of damage by both methods at entry, or remained undamaged. Of the remainder, 81% of the joints showed radiological damage first and 19% had clinical damage first. Development of radiological damage first was related to previous detection of swollen joints, and was inversely related to duration of arthritis. Conclusions: Radiological damage is often detected before clinical damage is observed. Clinical inflammation often precedes the detection of radiological damage.