Pain Mechanisms and Ultrasonic Inflammatory Activity as Prognostic Factors in Patients With Psoriatic Arthritis: A Prospective Cohort Study

OBJECTIVE: To study the prognostic value of widespread pain and of musculoskeletal ultrasound (US) examination for subsequent treatment outcomes in patients with psoriatic arthritis (PsA).METHODS: An exploratory prospective cohort study enrolled patients with PsA initiating biologic or conventional synthetic disease-modifying antirheumatic drugs in routine care. Clinical, US, and patient-reported measures were collected at baseline and after 4 months. Widespread nonarthritic pain (WP) was defined as a Widespread Pain Index score of ≥4 with pain in ≥4 of 5 regions. PsA activity by US was defined as color Doppler (yes/no) in selected entheses, joints, or tendons. The main response criteria included the American College of Rheumatology 20% improvement, the Disease Activity in Psoriatic Arthritis 50% improvement, and minimal disease activity. The primary analyses were age- and sex-adjusted logistic regression.RESULTS: WP was present in 24 of 69 included patients (35%) and was associated with worse patient-reported and composite baseline measures, while US and other objective findings were similar to those in patients without WP. The odds of reaching minimal disease activity after 4 months were significantly greater for patients enrolled without WP (odds ratio 18.43 [95% confidence interval 1.51, 224.41]; P = 0.022), while WP did not impair other response measures. Patients with baseline color Doppler activity (n = 42 [61%]) had a worse objective PsA burden, but their chance of treatment response was comparable to those without color Doppler.CONCLUSION: More than one-third of patients with PsA presented with WP, which was associated with worse patient-reported scores and failure to achieve minimal disease activity following conventional synthetic or biologic disease-modifying antirheumatic drug therapy. PsA activity by color Doppler US had no influence on subsequent treatment response in this PsA cohort.