Ultrasound assessment in psoriatic arthritis (PsA) and psoriasis vulgaris (non-PsA): which sites are most commonly involved and what features are more important in PsA?

BACKGROUND: The aim of this study was to find out the most commonly involved sites and the most important ultrasonic features in psoriatic arthritis (PsA). METHODS: In total, 120 PsA patients and 320 psoriasis vulgaris (non-PsA) patients were assessed by grayscale and power Doppler (PD) ultrasound (US). Joints, tendons, enthesis, and bursa changes were observed. Weights of affected anatomical sites of PsA patients (overall weights >90%) were calculated. Affected anatomical sites between PsA and non-PsA patients were compared. Ultrasonic features of joint, tendon, entheses, and bursa changes between PsA and non-PsA patients were also compared. Finally, the test performance of ultrasonic features for the diagnosis of PsA was calculated. RESULTS: The anatomical sites with the highest weights were the Achilles tendon, quadriceps tendon, and knee; weights of these anatomical sites were all more than 5%. Among the affected anatomical sites of PsA patients, most of the anatomical sites were more greatly affected in the PsA patients than in the non-PsA patients (all P<0.05). The comparison of the affected Achilles tendon, quadriceps tendon, MTP1, subacromial-subdeltoid bursa, MCP4, and MCP3 showed no significance between PsA and non-PsA patients (all P>0.05). Joint synovial thickening, joint PD signal grades, joint bone erosions, tendon sheath synovial thickening, tendon sheath PD signals, enthesis bone erosions, and enthesis PD signals in PsA patients were higher than in non-PsA patients (all P<0.05). Joint PD signal grades, joint bone erosions, enthesis bone erosions, and enthesis PD signals showed the highest specificities, which were 96.06%, 95.15%, 96.93%, and 94.63% respectively. CONCLUSIONS: The most common involvement sites of PsA were the Achilles tendon, quadriceps tendon, and knee, and some sites in non-PsA patients were also highly involved. The most important features in PsA included joint PD signal grades, joint bone erosion, entheses bone erosions, and entheses PD signals in US assessment.