Dactylitis Is Associated With More Severe Axial Joint Damage and Higher Disease Activity in Axial Psoriatic Arthritis

Objective To investigate the association of dactylitis with disease activity and the severity of damage detected by radiography in patients with axial psoriatic arthritis (axPsA). Methods Patients with axPsA who met the Classification Criteria for Psoriatic Arthritis were recruited. Clinical data, radiographic changes, and disease activity in patients with axPsA with or without dactylitis were compared using t tests, Mann-Whitney U tests, or Kruskal-Wallis tests for continuous variables. Chi-square or Fisher exact tests were used for categorical variables, and logistic regression analysis was performed to evaluate the association between dactylitis and damage detected by radiography. Results A total of 186 patients with axPsA were analyzed and dichotomized according to the presence or absence of dactylitis. Patients with dactylitis, as compared to those without dactylitis, had higher C-reactive protein ( P = 0.004), erythrocyte sedimentation rate ( P = 0.006), neutrophil-to-lymphocyte ratio ( P = 0.04), and platelet-to-lymphocyte ratio ( P = 0.02). In addition, patients with dactylitic axPsA, as compared to patients with nondactylitic axPsA, had higher tender joint counts, swollen joint counts, Disease Activity Index for Psoriatic Arthritis (DAPSA) scores, and Health Assessment Questionnaire scores ( P < 0.001). Patients with axPsA who had dactylitis, as compared to those who did not, also had higher values for the Disease Activity Score in 28 joints, Ankylosing Spondylitis Disease Activity Score, Bath Ankylosing Spondylitis Functional Index, and Bath Ankylosing Spondylitis Disease Activity Index ( P < 0.05), while fewer of these patients met the criteria for minimal disease activity and low disease activity ( P < 0.05). Consistently, they had more severe damage as detected by radiography ( P < 0.05), higher sacroiliac scores (odds ratio [OR] 2.08, 95% CI 1.14-3.79; P = 0.02), and a more significant reduction in bone mass density (OR 2.42, 95% CI 1.34-4.37; P = 0.003). No statistical differences were observed regarding HLA-B27 and the Leeds Enthesitis Index between these 2 groups of patients. Notably, only half of the patients with dactylitic axPsA had inflammatory back pain. Conclusion Our study demonstrated that patients with axPsA who had dactylitis had higher disease activity and more severe joint damage compared to those without dactylitis. Careful examination and proper management of axial involvement are recommended.