Prevalence of peripheral spondyloarthritis among patients with ultrasound-confirmed enthesitis: Single-center...

The primary goal of this study was to determine the prevalence of peripheral spondyloarthritis (pSpA) in patients with ultrasonography (USG)-confirmed enthesitis. The secondary aim of the study was to reveal the demographic, clinical, and ultrasonographic differences of patients diagnosed with pSpA.

Fifty-nine patients with USG-confirmed enthesitis were evaluated by a rheumatologist to evaluate if they met the Assessment of SpondyloArthritis International Society (ASAS) criteria for pSpA. Elementary lesions assessed by USG were based on the definition of the Outcome Measures in Rheumatology in Clinical Trials group which included hypoechogenicity, thickening, Doppler signal within 2 mm of bone, enthesophytes, bone erosions, and calcifications. For all patients, clinical and demographic data included: age, gender, smoking habits, body mass index, comorbid diseases, symptom duration, enthesitis region, the presence of bilateral enthesitis, entheseal pain visual analog scale (0-10), standardized enthesitis count following Maastricht Ankylosing Spondylitis Enthesitis Score (MASES) and SPondyloArthritis Research Consortium Canada (SPARCC) enthesitis index.

Eight (13.6%, 95% CI 6.0% to 25.0%) of 59 patients were diagnosed with pSpA according to the ASAS classification criteria. Participants diagnosed with pSpA had a longer duration of symptoms (54 vs 12 months), were more likely to present bilateral enthesitis (87.5% vs 49%) with higher SPARCC (11 vs 3) and MASES (6.5 vs 2) scores and higher C-reactive protein (7 vs 3.2 mg/L) concentrations. Entheseal Doppler signal and hypoechogenicity were also more frequently observed (50% vs 0% and 100% vs 49% respectively).

Peripheral SpA is not uncommon among patients presenting with enthesitis and more likely in cases with prolonged, extensive, and bilateral enthesitis with entheseal hypoechogenicity and Doppler signal. Musculoskeletal ultrasonography can facilitate the diagnosis of pSpA in patients presenting with enthesitis.