No-touch light test may help in monitoring scleroderma skin changes
Imaging tool potentially more effective, reliable than methods now used
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A noninvasive imaging technique, which uses light to look at skin tissue over a wide area without actually touching it, can reliably measure the extent of scarring, or fibrosis, in people with systemic sclerosis (SSc) — and may work better than measurements now in use in which clinicians track skin thickening by touch.
That’s according to a new study by U.S. researchers, which suggests that this tool, called spatial frequency domain imaging, or SFDI, could be used to help better monitor SSc — and track how hardening and thickening of the skin due to the rare condition progresses and responds to treatment.
The researchers noted that, currently, doctors can assess the same patient differently based on their own judgment of the extent of skin thickening.
“A fast, painless, non-contact measurement could help doctors track skin changes more objectively, help clinical trials detect treatment benefits more reliably and identify subtle skin changes before they can be felt by hand,” Andreea Bujor, MD, a professor at Boston University Chobanian & Avedisian School of Medicine and the study’s corresponding author, said in a university press release detailing its findings.
The study, titled “Spatial frequency domain imaging for assessment of skin fibrosis in systemic sclerosis: a prospective cohort study,” was published in the journal The Lancet Rheumatology. It involved patients and healthy adults from Boston Medical Center, where Bujor works as a rheumatologist, a doctor who specializes in chronic inflammatory conditions that affect the body’s connective tissues.
SSc, also known as scleroderma, occurs when the immune system becomes overactive and mistakenly attacks connective tissue. This causes excessive inflammation and fibrosis due to the overproduction of collagen, a structural protein. The disease’s symptoms can vary dramatically among patients, but often include thickened, hardened skin and numbness in the fingers and toes.
There are no approved treatments for SSc that specifically target the skin. Moreover, according to the study’s authors, researchers need objective ways to measure skin changes accurately and consistently when testing new treatments in clinical trials.
Many tools now used result in inconsistent findings, per the team. For example, the modified Rodnan skin score (mRSS) estimates how thick the skin is by touch, but it relies on a doctor’s judgment and may miss early or subtle changes.
Imaging test uses light, not touch, to assess skin
In this study, the scientists focused on SFDI, a technique that uses light to extract information about a tissue’s structure. Specifically, the team investigated whether or not SFDI could reflect fibrosis measured through clinical examinations and other imaging techniques.
The researchers suggested that “SFDI could complement existing clinical assessment and serve as an exploratory, centrally read outcome measure in future clinical trials.”
Altogether, their work involved 54 adults with systemic sclerosis and 30 healthy adults, who served as controls. The final analysis covered 49 patients and 25 controls, with biopsy samples — small pieces of skin collected for examination under a microscope — available from 34 people with SSc and 16 without.
Most of the patients (76%) had diffuse cutaneous systemic sclerosis, a disease type that can cause widespread thickening of the skin. About two-thirds had been diagnosed within the previous five years.
SFDI was used to measure two optical properties: diffuse reflectance, or the amount of light reflected from the skin, and the reduced scattering coefficient, which describes how strongly tissue scatters light. Both measurements were significantly lower in patients than in controls across all levels of clinically assessed skin, including sites where the mRSS was zero, the data showed.
“We compared the light readings directly with the amount of collagen buildup in skin biopsies, linking the imaging measurements to the scarring in the skin. We also compared the readings with ultrasound skin thickness and the standard clinical skin score, tested how repeatable the measurements were, and examined whether they changed as patients’ skin changed over time,” Bujor said.
In patients, a higher mRSS was associated with a lower diffuse reflectance and scattering coefficient. When measurements from six sites across the hands, forearms and fingers were combined, both diffuse reflectance and scattering coefficient showed moderate relationships with the overall severity of the disease.
This is first time tech was applied in scleroderma
Biopsy samples provided further evidence that SFDI reflects underlying changes in the tissue’s structure, the team noted.
Optical measurements were associated with several signs of fibrosis, including increased collagen, increased alpha-smooth muscle actin — a protein abundant in activated scar-forming cells — and eccrine gland entrapment, in which sweat glands become surrounded by scar tissue.
SFDI measurements also showed moderate relationships with thickness measured by ultrasound of the skin, but little relationship with stiffness measured by a durometer, which measures the hardness of the skin.
In a follow-up analysis involving 11 patients, changes in SFDI measurements were associated with changes in mRSS over time. Lab testing also showed high consistency between different researchers and repeated measurements, suggesting that SFDI can be reliable.
These findings support further development of SFDI as an objective, non-contact, … biologically anchored approach for assessing skin involvement in systemic sclerosis.
Overall, according to the scientists, SFDI appears to be a promising, objective way for measuring involvement of the skin in SSc.
“We have been developing SFDI for almost 15 years in my lab, but this is the first time anyone has applied this technology to scleroderma,” said Darren Roblyer, PhD, a professor of biomedical engineering at Boston University and one of the authors of the study.
The researchers noted that larger studies are needed to validate SFDI. Still, “by successfully distinguishing disease states, detecting subclinical involvement, and tracking longitudinal change, SFDI emerges as a promising next-generation biomarker for clinical trials and routine patient monitoring,” the team wrote.
Per the team: “These findings support further development of SFDI as an objective, non-contact, … biologically anchored approach for assessing skin involvement in systemic sclerosis.”
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