SPATIAL frequency domain imaging (SFDI), a non-contact optical method, has emerged as a potential objective measure of skin fibrosis in systemic sclerosis, according to a new prospective cohort study.
Systemic sclerosis is an autoimmune disease with no approved skin-directed therapies, and the modified Rodnan skin score (mRSS), the standard measure of skin involvement, has limitations. A non-invasive, objective and scalable measure of skin fibrosis in systemic sclerosis suitable for multicentre trials was lacking.
This single-centre, prospective cohort study was conducted at Boston Medical Center (Boston, MA, USA). Between October 2019 and June 2025, 54 patients with systemic sclerosis and 30 controls without autoimmune disease were enrolled; 49 and 25 respectively were analysed, with biopsies from 34 and 16.
Among those analysed, 78% of patients and 80% of controls were female, and mean age was 50 and 49 years respectively. Assessments included SFDI, mRSS and optional forearm biopsy, with follow-up every 3 months in year one and every 6 months thereafter for 3 years in the expanded phase.
Main analyses assessed baseline associations of diffuse reflectance (Rd) and reduced scattering coefficient (μs′) with mRSS, and correlations with histological dermal fibrosis.
Rd and μs′ were significantly lower in patients with systemic sclerosis than in controls across all mRSS strata, including sites where mRSS was 0.
Each one-point increase in local mRSS was associated with decreases in Rd (β: −0.0028; 95% confidence interval [CI]: −0.0050 to −0.0006; p=0.014) and μs′ (β: −0.0158; 95% CI: −0.0314 to −0.0003; p=0.047).
SFDI correlations were weak to moderate with mRSS (r: −0.48 to −0.38) and moderate with histological fibrosis (r: −0.52 to −0.34).
These findings have suggested that SFDI provides an objective, non-invasive measure of skin involvement that aligns with established assessments, supporting its potential as a quantitative outcome measure for evaluating skin disease, consistent with Outcome Measures in Rheumatology principles.
Reference
Vo H et al. Spatial frequency domain imaging for assessment of skin fibrosis in systemic sclerosis: a prospective cohort study. Lancet Rheumatol. 2026;DOI:10.1016/S2665-9913(26)00229-8
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