A Seven-Joint Ultrasound Score for Differentiating Between Rheumatoid and Psoriatic Arthritis

Differentiating between seronegative rheumatoid arthritis (RA) and psoriatic arthritis (PsA) presenting only with the involvement of the small joints of the hands can be challenging. Implementing musculoskeletal ultrasound (US) to reveal specific patterns of joint and tendon involvement may have an added value in the management of early arthritis.

The aim was to investigate whether a seven-joint US score was able to distinguish between patients with RA and PsA.

One hundred and forty-one patients with RA, 65 patients with PsA, and 45 healthy controls (HC) were included in the current study. US assessment of the wrist, second and third metacarpophalangeal, second and third proximal interphalangeal joint, second and fifth metatarsophalangeal joint was performed, and the following scores were calculated: synovitis and tenosynovitis/ paratenonitis scores on grayscale ultrasound (GSUS) and on power Doppler (PD) US, erosion score, US7 score.

RA patients had significantly higher median scores of GS synovitis, PD synovitis, erosions, and US7 than PsA patients (p < 0.001). PsA patients had significantly higher median scores of GS tenosynovitis/paratenonitis and PD tenosynovitis/paratenonitis (p < 0.001). All US scores were significantly higher for both patient groups as compared to the HC group (p < 0.001).

Sonographic evaluation by a seven-joint score can be helpful in the differentiation between rheumatoid and psoriatic arthritis.