Background Enthesitis is a common clinical feature of spondyloarthritis (SpA) that could be evaluated by ultrasound (US). Some studies suggested that US assessment of enthesitis might be sensitive and specific of SpA diagnosis. However, others studies found similar prevalence of US enthesitis in rheumatoid arthtitis (RA) and SpA (1) or that US assessment of heels could not differentiate SpA to controls (2).

Objectives We aimed to determine the prevalence of US enthesitis in SpA and RA patient.

Methods In this transversal single center study, we included patient with RA (ACR/EULAR 2010 criteria) and SpA (ASAS criteria). All patients underwent clinical and ultrasonographic evaluation of both upper and lower limbs at seven sites (quadriceps tendon enthesis, proximal and distal patellar tendon enthesis, Achilles tendon enthesis, plantar aponeurosis enthesis, triceps tendon enthesis, lateral epicondyle enthesis). Two US scores were calculated for each patient using the Glasgow Ultrasound Enthesitis Scoring System (GUESS) and the Madrid Sonographic Enthesitis Index (MASEI). US assessment of tendon thickness and structure, bone erosion, bursitis, power Doppler, calcifications and enthesophytes was performed for all patients by a sonographer blinded to clinical data. Demographic and clinical characteristics were collected for each patient.

Results A total of 30 RA (mean age: 45.3±15.4 years old, 17% of male patients, mean disease duration: 10.5±7.9 years) and 41 SpA (mean age: 55.7±14.8 years old, 68% of male patients, mean disease duration: 9.2±8.7 years) patients were analyzed. In SpA patients, 67% of them were HLAB27 positive. ACPA and rheumatoid factor were found in 93% and 83% of RA patients, respectively. Clinical examination found painful enthesis in 98 (17%) of 574 examined sites in SpA patients and in 59 (14%) of 420 sites in RA (P=0.2). SpA and RA patients had 2.4 and 1.96 painful enthesis sites per patients, respectively (P=0.81). The mean MASEI score was 8.5±7.3 in RA and 7.8±6.5 in SpA patients (P=0.87). A MASEI score ≥18 was found in 6 (20%) RA patients and in 4 (10%) of SpA patients (P=0.22). The mean GUESS score was 5.8±3.1 in RA and 6.3±3.9 in SpA patients (P=0.67). At least one enthesis abnormality was found by US in 264 (46%) of 574 sites in SpA patients and in 200 (48%) of 420 sites in RA (P=0.61).

Conclusions Our results suggest that entheseal abnormalities are frequent in RA and SpA without difference in the population. We could hypothesize that the US assessed entheseal features have low specificity in inflammatory conditions affecting joints and enthesis as SpA and RA.

1. Genc H, Cakit BD, Tuncbilek I, Erdem HR. Ultrasonographic evaluation of tendons and enthesal sites in rheumatoid arthritis: comparison with ankylosing spondylitis and healthy subjects. Clin Rheumatol. 2005 Jun;24(3):272–7.

2. Feydy A, Lavie-Brion MC, Gossec L, Lavie F, et al. Comparative study of MRI and power Doppler ultrasonography of the heel in patients with spondyloarthritis with and without heel pain and in controls. Ann Rheum Dis. 2012 Apr;71(4):498–503

Disclosure of Interest None declared