Reliability of Ultrasound and Elastography in the Assessment of Skin Involvement in SSc

Ultrasound may be a valid and reliable tool for measuring skin thickness in patients with systemic sclerosis (SSc); however significant knowledge gap remain in this area, according to findings of a systematic literature review published in Seminars in Arthritis and Rheumatism.

The authors performed a systemic literature review within the Skin Ultrasound Working Group of the World Scleroderma Foundation. They searched fulltext articles published in any language that included adult patients and the assessment of ultrasound to quantify skin pathology in SSc, using the participants, intervention, comparator, and outcomes (PICO) framework. An assessment of risk of bias, data extraction, and synthesis were independently performed by 2 reviewers.

Of the 3248 references evaluating skin ultrasound and elastography between January 1979 and May 2021, 46 were included in the current review. Overall, B-mode ultrasound, elastography, or both, were used in 30 (62.5%), 9 (19.6%) and 7 (15.2%) studies, respectively. The outcome measure domains reported for ultrasound were thickness (57.8%) and echogenicity (17.2%), while stiffness (25%) was the domain reported for elastography.

The authors observed high heterogeneity and frequent underreporting of the methods used for image acquisition and analysis. For example, information on probes’ frequency, number and precise definition of skin sites assessed, skin layers evaluated, scoring system, and blinding, was lacking. Similar issues of heterogeneity and underreporting existed for contextual factors and feasibility.

The authors also noted good evidence for reliability and convergent validity of skin thickness evaluations compared with modified Rodnan skin scores, but limited evidence for validity of stiffness and echogenicity measurements against histologic findings. For the reported ultrasound domains, limited evidence was observed for sensitivity to change, test-retest reliability, clinical trial discrimination, and thresholds of meaning.

The authors of the review concluded, “Standardization of procedures and reporting seems, therefore, a crucial step to further develop and consolidate the contribution of ultrasound skin evaluation in SSc, together with research focused on the knowledge gaps identified herein.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference

Santiago T, Santos E, Ruaro B, et al. Ultrasound and elastography in the assessment of skin involvement in systemic sclerosis: A systematic literature review focusing on validation and standardization. Semin Arthritis Rheum. Published online January 10, 2022. doi:10.1016/j.semarthrit.2022.151954