033 Ultrasound (US) features of psoriatic arthritis (PsA): observations from an early inflammatory arthritis (EIA) diagnostic service

Background: To ensure a rapid diagnosis of EIA several rheumatology centres have developed diagnostic US services to detect sub-clinical features and subsequently implement treatment plans early. Though most of these services have developed scanning protocols designed to detect early rheumatoid arthritis, the EIA patients seen are commonly diagnosed with other inflammatory arthritides such as early PsA. The evidence base for what constitutes US features of PsA is emerging which will hopefully inform on what the optimal screening US sequence for PsA will be. We assessed what characteristic US abnormalities were seen in patients diagnosed with PsA from our EIA diagnostic service. Methods: We conducted a retrospective review of patients seen in the EIA US diagnostic service at Croydon Health Services NHS Trust; patients diagnosed with PsA (CASPAR criteria) who had an US scan between Oct 2017-Sept 2018 were included. Images and reports were reviewed. Greyscale (GSUS) and Power Doppler (PDUS) abnormalities, erosions, enthesitis, dactylitis, paratenonitis/peritendinitis and tendonopathies/tenosynovitis were defined according to OMERACT definitions. Results: 48 patients with PsA had a diagnostic US in the EIA diagnostic service during the study time. The body areas scanned were as follows: 48 hands (DIPJs,PIPJs,MCPJs,extensor & flexor tendons) and wrists (ulnar-carpal-joint,radiocarpal-joint & extensor tendons), 25 feet (MTPJs,midtarsals & tibio-talar joint), 36 epicondyles,supra/infrapatellar,achilles & plantar fascia). GSUS (grade2-3) was found in 17% with PIPJs,wrists,midtarsals and MTPJs being the commonest affected with PDUS (grade1-3) in 12.5% (PIPJs,wrists and MTPJs). No erosions were seen. Mild-moderate dactylitis was seen in 4.2% (2/48) patients. Juxta-articular enthesytes were seen in over 4/5 patients in DIPJs & PIPJs. Of the 36 who had entheseal assessments, enthesitis was seen in 39% (14/36) in the epicondylar regions, 25%(9/36) supra/infrapatellar regions and 58% (21/26) achilles/plantar fascia). More than 1/3 had changes in 2-or-more entheseal regions. Paratenonitis was seen in 48% (23/48) exclusively in PIPJs. Tendonopathic changes were seen in 58% (28/48) predominantly in extensor tendon groups. 83% (40/48) had 2-or-more combination features of juxta-articular enthesytes, enthesitis, paratenonitis or tendonopathic changes. Conclusion: Our observational study found that early PsA patients seen in the EIA US diagnostic service in Croydon presented with US characteristics that were different in many respects to that expected in RA protocols. Tendonopathic features (especially in the extensor tendons), juxta-articular enthesytes, paratenonitis and enthesitis seem to be more commonly seen compared to GSUS and PDUS synovitis. Furthermore, it was common to see combinations of entheseal, paratenon and tendonopathic US features (>80%). No erosive changes were seen and there was a scarcity of dactylitis. It is essential therefore, that EIA US diagnostic services adapt their screening protocols to encompass more articular and entheseal areas with a particular focus on entheseal, paratenon and tendon regions to improve the diagnostic sensitivity for early PsA. Disclosures: R. Rajak: None. M. Sharif: None. F. Sheikh: None. S. Levy: None. R. Suresh: None. R. Sathananthan: None. N. Horwood: None.