Spatial Frequency Domain Imaging Offers Objective Collagen Assessment in Scleroderma, Lancet Rheumatology Study Shows

Researchers at Boston University applied SFDI, which projects patterned light and analyzes diffuse reflectance, to 49 scleroderma patients and 25 controls. Readings differed significantly between groups and tracked clinical skin scores, ultrasound thickness, and histologic fibrosis in 50 forearm biopsies. Repeat measurements in 11 patients over time aligned with changes in manual scores, indicating potential for serial monitoring without skin contact. The technique also flagged abnormalities in areas scored normal by palpation, suggesting earlier detection of subclinical fibrosis.

Manual skin scoring has served as the primary endpoint in scleroderma trials for decades yet shows high inter-rater variability that can mask modest treatment effects. SFDI addresses this by providing quantitative optical properties linked directly to collagen density. Prior SFDI validation in burn and wound healing studies demonstrated repeatability within 5 percent across operators, supporting its extension to autoimmune fibrosis where objective metrics remain scarce.

No approved antifibrotic therapies exist for skin involvement, partly because subjective endpoints obscure trial signals. If SFDI reduces measurement noise, future randomized studies could detect smaller effect sizes and shorten enrollment periods. Remaining questions include performance across skin phototypes and correlation with internal organ progression, both required before regulatory acceptance as a surrogate endpoint.

The study design was prospective and multi-modal but single-center with modest sample size; next steps require multicenter validation and linkage to long-term clinical outcomes.