Ultrasound nail assessment in patients with psoriasic arthritis: is there an association of findings with clinical scores?

Background: Psoriatic arthritis can involve several domains. Due to its multifaceted nature and its frequent comorbidities such as depression, obesity, osteoarthritis and fibromyalgia, it is difficult to monitor these patients because the clinical scores involve subjective data. High-resolution ultrasound probes allowed the evaluation of more superficial structures, such as the nails and their synovio-entheseal framework, in close relationship with the enthesis of the distal extensor digitorum tendon. Nail ultrasound studies vary in terms of the parameters and fingers studied and in their findings.

Objectives: To describe the most significant sonographic nail changes and the most affected fingers in psoriatic arthritis and to verify the association of nail ultrasound findings with clinical scores (nail psoriasis severity index (NAPSI), ankylosing spondylitis disease activity score with C-reactive protein (ASDAS-CRP), minimal disease activity (MDA), disease activity index for psoriatic arthritis (DAPSA)).

Methods: This was a cross-sectional study with 52 patients with psoriatic arthritis at the Hospital de Clínicas do Paraná and 50 controls. A total of 1016 nails were analyzed (517 from patients with psoriatic arthritis and 499 from controls). Ultrasonography of the nails of the 10 fingers was performed to assess the trilaminar appearance, measure the distance from the nail bed, identify synovitis of the distal interphalangeal joints and the presence of a power Doppler signal from the nail matrix/nail bed. The captured images were independently evaluated by a rheumatologist with expertise in musculoskeletal ultrasound. Data analysis was performed using IBM SPSS Statistics v.28.0.0 software, and the association of nail plate changes, nail bed distance and power Doppler signal with the NAPSI, DAPSA, MDA and ASDAS-PCR were calculated. Spearman correlation coefficients were estimated to analyze the correlations between pairs of quantitative variables. Student's t test and the Mann‒Whitney U test were used to compare quantitative variables, and Fisher's exact test was used to compare categorical variables between patients and controls. The nonparametric Mann‒Whitney U and Kruskal‒Wallis tests were used to compare groups according to the MDA or DAPSA classification.

Results: The Doppler signal of the nail matrix and nail bed was more frequently identified in patients (44.2%) than in controls (6%), and the difference in the mean power Doppler signal between the two groups was significant (p < 0.001). Changes in the nail plate were more common in the right thumb (44.2%), left thumb (36.5%) and second finger on the right hand (32.7%). The number of fingers with nail plate changes, enthesitis, paratendinitis, grayscale synovitis and DIP involvement in the distal interphalangeal joints was higher among patients with psoriatic arthritis (p < 0.001). There were found some correlations between US findings and clinical scores: ultrasound nail involvement and the NAPSI score (p = 0.034), the number of fingers and mean change in the nail plate and the ASDAS-CRP (p = 0.030). DAPSA (remission/low activity versus moderate/high activity) was associated to the mean change in the nail plate (p < 0.013).

Conclusions: Nail ultrasound has the potential to assist in the capturing of the actual disease activity status in patients with psoriatic arthritis.