Researchers from the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) examining ultrasound scoring instruments for the assessment of enthesitis in psoriatic arthritis (PsA) found that despite development of multiple ultrasound scoring systems for use in spondyloarthritis (SpA), most have not been validated for PsA and none passed the PsA Outcome Measures in Rheumatology (OMERACT) filter, according to findings published in The Journal of Rheumatology.

Most ultrasound scoring instruments have focused on SpA rather than PsA, without offering information about patient-level entheseal burden. Investigators sought to evaluate the validity of musculoskeletal ultrasound instruments and identify knowledge gaps that require the further development of tools for the diagnosis and management of PsA-related enthesitis.

A systematic literature review searched the Cochrane, EMBase and PubMed databases for studies involving enthesitis, ultrasound, PsA, or SpA. Researchers extracted data on the properties of the sonographic enthesitis instruments used in each study following components of the OMERACT filter, including feasibility, reliability, validity, and treatment response.

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From a total of 310 full-text studies, 51 were selected for further analysis, of which 35% assessed patients with PsA specifically. The remaining manuscripts involved SpA (33%), ankylosing spondylitis (19.6%), psoriasis (9.8%), and juvenile idiopathic arthritis (1 study). Most reports (88.2%) included Doppler evaluation as part of their ultrasound instruments.

There was only a single ultrasound enthesitis scoring tool (PsASon-score) developed and validated specifically for PsA. In the 8 (15.6%) reports that included feasibility, the time needed to assess entheses ranged from 15 to 90 minutes. Biomarker-related construct validity was analyzed in only 1 (2%) study, while clinical examination was used for this purpose in 11 (21.5%) studies. None of the trials used imaging to analyze construct validity. In addition, there were only 2 (4%) studies that explored PsA discriminative validity, and in 7 (13.7%) that looked at treatment responsiveness, none were conducted on PsA populations.

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Major limitations of the studies in the analysis included lack of standardization across trials and knowledge gaps regarding validity in PsA enthesitis. In addition, all but 1 instrument were developed for use in axial SpA rather than PsA, most studies used small samples, instruments were based on expert opinion vs hard data, and a wide variation of entheseal sites existed across studies, with most focusing on the lower extremities. Scoring instruments were also limited in terms of identifying active vs inactive disease and evaluating treatment responsiveness.

The authors noted that, “some of these instruments have been validated in patients with SpA; however, the validity of these tools in PsA is largely unknown.” They also added, “There is a need for a well-validated instrument for assessment of sonographic enthesitis in PsA that includes the unique features of PsA and will assist in diagnosis, disease burden quantification, clinical decisions, and prognosis.”

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Elalouf O, Ureyen SB, Touma Z, et al. Psoriatic arthritis sonographic enthesitis instruments: a systematic review of the literature. J Rheumatol. 2018;45(7):1-14.