Utility of musculoskeletal ultrasound in Psoriatic Arthritis

Purpose
Psoriatic arthritis (PsA) is a chronic autoimmune disease that causes a variety of musculoskeletal abnormalities. Musculoskeletal ultrasound in PsA is becoming increasingly popular, both in clinical practice and research. The aim of this
narrative review is to evaluate recent literature on the utility of ultrasound in PsA.

Methods
In total, 178 publications in English from Pubmed with “psoriatic arthritis” and either “ultrasound”, “ultrasonography”, or “sonographic” in the title were reviewed and publications with similar findings were grouped together into a total of seven domains.

Findings
Overall, 40 studies investigated the use of ultrasound in various aspects of PsA. Publications that were not relevant (n=59), were not original research (n=45), or that had small sample sizes (<30) (n=34) are not discussed. Key findings were grouped into seven themes: 1) the use of ultrasound findings compared to clinical assessment; 2) the use of ultrasound in the assessment of enthesitis; 3) the use of ultrasound in the assessment of nails; 4) the use of ultrasound as a screening tool for patients with psoriasis at risk of developing PsA; 5) the use of ultrasound in differentiating PsA from other similar conditions; 6) the use of ultrasound as a measure of disease activity; and 7) the use of ultrasound compared to MRI.

Implications
Recent studies have shown that ultrasound measures of inflammation tend to agree with objective clinical findings of disease such as swollen joint counts, whilst being less influenced by subjective measures such as pain. Ultrasound has
utility in the assessment of enthesitis, and psoriatic nail disease in PsA, and as an overall measure of disease activity. Ultrasound-based outcome measures have been used in observational studies and in clinical trials involving PsA and may have utility as a measure of treatment response. Furthermore, recent studies suggest that ultrasound may have utility in improving the accuracy and precision of screening programmes designed to identify subclinical PsA in cohorts of patients with psoriasis; however, cost-efficacy remains to be determined. Beyond screening, ultrasound may also have utility in aiding diagnosis of PsA in patients with suspected inflammatory arthritis. Finally, studies suggest that ultrasound measures of inflammation agree with magnetic resonance imaging measures of inflammation, meaning incorporating ultrasound into clinical practice can overcome barriers associated with MRI scanning. As ultrasound technology continues to advance, and associated costs decrease, it is likely that ultrasound will be more integrated into the clinical journeys for patients with PsA.