Enthesitis in patients with psoriatic arthritis and axial spondyloarthritis - data from the Danish nationwide DANBIO registry.

Objective: To explore the registration, pattern and burden of clinical enthesitis among routine-care patients with psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA) in the Danish nationwide DANBIO registry.

Methods: In patients with PsA and axSpA in DANBIO, prospectively registered data from 2010 to 2020 on clinical entheseal assessment using SPARCC score were compared with demographic, clinical and patient-reported-outcome (PRO) data.

Results: 6582 PsA and 5547 axSpA patients had their first registration in DANBIO in 2010 or later ("incident cohort"). At these registrations, 1037 (16%) PsA and 1188 (21%) axSpA patients had entheseal assessments, with ≥1 enthesitis being found in 66% and 39%, respectively. Mean enthesitis scores were 2.5 (PsA) and 1.3 (axSpA). Most common sites were: Achilles tendon (right/left/symmetrical: PsA:24.4%/23.3%/17.1%; axSpA:10.4%/10.6%/8.0%), lateral epicondyle (PsA:22.2%/20.1%/16.2%; axSpA:.4%/9.7%/7.6%), plantar fascia (PsA:17.1%/17.0%/12.6%; axSpA:10.4%/10.6%/8.0%), greater trochanter (PsA:14.2%/15.4%/11.7%; axSpA:9.9%/11.2%/8.2%). Enthesitis was more frequent in women (PsA/axSpA 61%/62%) than men (39%/37%). Patients with vs without enthesitis had higher overall burden (higher physician global, swollen/tender joint counts, pain, fatigue, patient global; fewer in patient-acceptable-symptom-state (PASS)) (all p < 0.05). Comparable demographic, clinical and PRO-results in patients with missing entheseal assessments, support the data being representative. In an "overall" cohort of all patients with ≥1 entheseal assessments after 2010, results on enthesitis were comparable.

Conclusion: Entheseal assessments were only performed at a minority of clinical visits. Clinical enthesitis was frequent, particularly in women, often symmetrical and associated with a higher physician- and patient-reported disease burden in patients with PsA and axSpA treated in routine practice, emphasizing the need for systematic assessment in routine care.