To assess the performance of various sonographic elemental entheseal lesions in distinguishing between psoriatic arthritis (PsA) and controls to inform the development of a novel sonographic enthesitis score for PsA.
A total of 100 age- and sex-matched individuals (50 PsA and 50 controls) were evaluated. Eleven entheseal sites were scanned bilaterally according to a standardized protocol by 2 sonographers. Based on the Outcome Measures in Rheumatology (OMERACT) definition of sonographic enthesitis, the following lesions were assessed: structural entheseal changes (hypoechogenicity), thickening, bone erosion, enthesophytes, calcification, and Doppler signal, in addition to bursitis and bone irregularities. The images were read by 2 readers blinded to the clinical information. A series of logistic regression models were used to find the optimal combination of entheseal sites and elementary lesions that distinguished PsA from controls.
Mean age was 55 ± 10 years (59% males). The optimal model that distinguished PsA from controls included 5 elementary lesions (enthesophytes, Doppler signal, erosions, thickening, and hypoechogenicity) and 6 entheseal sites (patellar ligament insertions into the distal patella and tibial tuberosity, Achilles tendon and plantar fascia insertions into the calcaneus, common extensor tendon insertion into lateral epicondyle, and supraspinatus insertion into the superior facet of the humerus). The area under the receiver-operating characteristic curve for this model was 0.93 (95% CI 0.88–0.98).
We identified potential elemental ultrasonographic abnormalities and entheseal sites that could distinguish PsA and controls. This information will contribute to the development of a new sonographic score for assessment of enthesitis in patients with PsA.