Value of ultrasound-assessed dactylitis in the early diagnosis of psoriatic arthritis.

Purpose: The primary objective of this prospective, longitudinal, observational, single-centre study was to evaluate the association between ultrasound-assessed lesions of dactylitis and the diagnosis of psoriatic arthritis (PsA) in patients with psoriasis (PsO) and hand arthralgia.

Methods: We included adult patients diagnosed with PsO with hand arthralgia, with or without other musculoskeletal complaints. They were clinically assessed at baseline, 6 and 12 months by a rheumatologist blinded to the ultrasound findings. At baseline, patients underwent a B-mode (BM) and power Doppler (PD) ultrasound assessment by other rheumatologist blinded to clinical data. The ultrasound evaluation included bilateral detection and scoring of synovitis (3 joints, 0-3), tenosynovitis (flexor tendons, 0-3), enthesitis (9 sites, 0-1), peri‑extensor tendon inflammation (PETI) (0-3), and subcutaneous tissue inflammation (SCTI) (0-3) in the 2nd-5th fingers.

Results: Seventy patients [44 women; mean (SD) age 51 (12.4) years] were included, of whom 64 completed the study. Of these, 15 (23.4 %) were diagnosed with PsA during the 12-month follow-up period. At finger level, the presence and amount of baseline BM and PD synovitis, BM tenosynovitis, BM and PD enthesitis, and BM and PD PETI were associated with PsA diagnosis (p < .05). A predictive model including two variables, presence of PD synovitis and BM enthesitis, was found to predict PsA diagnosis (χ2 = 35.38; p < .001) with an accuracy of 89.1 %, a sensitivity of 86.7 % and a specificity of 89.8 %.

Conclusions: Ultrasound-assessed lesions of dactylitis were associated with a diagnosis of PsA and the short-term development of PsA in patients with PsO and hand arthralgia.