OBJECTIVES: To assess, in spondyloarthritis (SpA), the discriminative value of the Outcome Measures in Rheumatology (OMERACT) ultrasound lesions of enthesitis and their associations with clinical features in this population. METHODS: In this multicentre study involving 20 rheumatology centres, clinical and ultrasound examinations of the lower limb large entheses were performed in 413 patients with SpA (axial SpA and psoriatic arthritis) and 282 disease controls (osteoarthritis and fibromyalgia). 'Active enthesitis' was defined as (1) power Doppler (PD) at the enthesis grade ≥1 plus entheseal thickening and/or hypoechoic areas, or (2) PD grade >1 (independent of the presence of entheseal thickening and/or hypoechoic areas). RESULTS: In the univariate analysis, all OMERACT lesions except enthesophytes/calcifications showed a significant association with SpA. PD (OR=8.77, 95% CI 4.40 to 19.20, p<0.001) and bone erosions (OR=4.75, 95% CI 2.43 to 10.10, p<0.001) retained this association in the multivariate analysis. Among the lower limb entheses, only the Achilles tendon was significantly associated with SpA (OR=1.93, 95% CI 1.30 to 2.88, p<0.001) in the multivariate analyses. Active enthesitis showed a significant association with SpA (OR=9.20, 95% CI 4.21 to 23.20, p<0.001), and unlike the individual OMERACT ultrasound lesions it was consistently associated with most clinical measures of SpA disease activity and severity in the regression analyses. CONCLUSIONS: This large multicentre study assessed the value of different ultrasound findings of enthesitis in SpA, identifying the most discriminative ultrasound lesions and entheseal sites for SpA. Ultrasound could differentiate between SpA-related enthesitis and other forms of entheseal pathology (ie, mechanical enthesitis), thus improving the assessment of entheseal involvement in SpA.

Department of Health Promotion Mother and Child Care Internal Medicine and Medical Specialties Rheumatology Section University of Palermo Palermo Italy

Department of Internal Medicine Provincial Hospital Madonna del Soccorso San Benedetto del Tronto Italy

Department of Medicine Internal Medicine and Rheumatology Unit Azienda Ospedaliero Universitaria di Parma Parma Italy

Department of Paediatric and Adult Rheumatology Motol University Hospital Praha Czech Republic

Department of Precision and Regenerative Medicine and Ionian Area Rheumatology Unit University of Bari Bari Italy

Department of Rheumatology and Immunology Guangdong Provincial People's Hospital Southern Medical University Guangzhou Guangdong China

Department of Rheumatology Iuliu Haţieganu University of Medicine and Pharmacy Cluj Napoca Romania

Department of Rheumatology School of Health Sciences University of Ioannina Faculty of Medicine Ioannina Greece

Department of Rheumatology Servicio Integral de Reumatología e Inmunología Doctor Orlando Villota Pasto Colombia

Department of Rheumatology The Hokkaido Medical Center Sapporo Japan

Division of Rheumatology Fundación Hospital San Pedro San Juan de Pasto Colombia

Division of Rheumatology Hacettepe University Faculty of Medicine Ankara Turkey

Division of Rheumatology National Institute of Rehabilitation Luis Guillermo Ibarra Ciudad de Mexico Mexico

Faculty of Health Sciences University of Beira Interior Covilha Portugal

Guangdong Cardiovascular Institute Guangdong Provincial People's Hospital Guangdong Academy of Medical Sciences Guangzhou Guangdong China

Instituto de Rehabilitación Psicofísica Buenos Aires Argentina

Leeds Institute of Rheumatic and Musculoskeletal Medicine University of Leeds Leeds UK

Rheumatology Department Centro Hospitalar e Universitário de Coimbra EPE Coimbra Portugal

Rheumatology Department Hospital Juárez de México Mexico City Mexico

Rheumatology Department Leiria Hospital Centre Pousos Portugal

Rheumatology Hospital San Roque de Gonnet La Plata Buenos Aires Argentina

Rheumatology Unit Department of Clinical and Molecular Sciences 'Carlo Urbani' Hospital Polytechnic University of Marche Ancona Italy

Rheumatology Unit Department of Internal Medicine Hospital Italiano de Buenos Aires Buenos Aires Argentina

Rheumatology Unit Hospital Universitari Vall d'Hebron Barcelona Spain

Rheumatology Unit IRCCS Azienda Ospedaliero Universitaria di Bologna Policlinico di Sant'Orsola Bologna Italy

Rheumatology Unit University of Cagliari Cagliari Italy

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