Grant: Travel Awards - Institute Community Support

Methods: Patients with psoriatic arthritis were recruited from the University of Toronto prospective observational PsA cohort. Patients fulfilled the CASPAR criteria and were assessed every 6-12 months according to a standard protocol which included a detailed history, physical examination and laboratory evaluation. Radiographs of peripheral joints and spine were obtained every 2 years. DISH was defined as flowing bony bridges in at least 4 contiguous thoracic vertebrae irrespective of the presence of radiographic sacroiliitis. Each PsA patient with DISH was matched by sex to three PsA patients without DISH from the same cohort who were recruited to the clinic within the same time period. Demographics and disease characteristics were compared in both groups. The radiographic features that were assessed included the presence of sacroiliitis, syndesmophytes and calcaneal spurs. Descriptive analyses and comparison were conducted using McNemar test, Fisher's Exact test and Chi-squared test for Categorical variables and paired t-test for continuous variables. Results: Of 938 PsA patients, the prevalence of DISH was 8.3%. Patients with DISH were older (62.9 vs 49.3, P<0.0001), had a longer disease duration (15.1 vs 12.8 years, P<0.0001), a higher BMI (32.9 vs 28.7, P<0.0001), more diabetes (28% vs 9.8%, P<0.0001), hypertension (50% vs 24.9%, P<0.0001) and higher uric acid levels (16% vs 7%, P=0.02). The Steinbrocker score was also higher in patients with DISH (32.0 ± 39.8 vs 19.5 ± 31.4, P=0.0001). The presence of inflammatory back pain, HLA-B*27 allele and sacroiliitis was similar in both groups. The difference in ESR and CRP was not clinically relevant. However, patients with DISH had more syndesmophytes (38.5% vs 18.7%, P<0.0001) and calcaneal spurs (83.3% vs 60.9%). Conclusions: DISH was associated with known DISH related factors including diabetes mellitus and increased BMI. The diagnosis of DISH is possible in the presence of psoriatic spondylitis.