Fluorescence-optical imaging (FOI) identified early signs of psoriatic arthritis, based on data from 2 years of follow-up of a cohort of 389 adults at 14 rheumatology centers.
Approximately 25% of individuals with psoriasis go on to develop psoriatic arthritis (PsA), but there are no validated biomarkers to identify patients at risk for progression to PsA, Michaela Koehm, MD, of Goethe University, Frankfurt am Main, Germany, and colleagues wrote in RMD Open.
FOI is a technique that allows assessment of changes in microvascularization and subdermal skin inflammation, and because individuals with psoriasis who develop PsA have shown changes in blood vessel formation in the early stages of disease, the researchers sought to determine if FOI could be used to predict early PsA.
The researchers conducted a multicenter, two-part observational cohort study. The two parts, known as XCITING and XTEND, included 389 adults aged 18-75 years with plaque psoriasis deemed at increased risk for PsA. The patients were seen at rheumatology sites in Germany between Jan. 28, 2014, and March 16, 2017. The XTEND study included clinic visits 18-24 months after the XCITING study.
Participants underwent a complete clinical examination, with musculoskeletal ultrasound (MSUS) and FOI on both hands at a single visit. Those with positive FOI findings not seen with clinical exam or MSUS underwent MRI within 7 days. Patients with positive FOI but negative findings on clinical exam, MSUS, and MRI were followed for 2 years in the XTEND study.
The primary outcome was the ability of FOI to detect musculoskeletal inflammation, compared with clinical examination and MSUS.
Overall, 50% of the patients were diagnosed with PsA. A total of 116 (30%) had positive FOI findings; complete MRI data were available for 108 of these patients, including 68 negative MRIs and 40 positive MRIs.
In the XTEND study, another 12% of patients who were positive on FOI but not on MRI also developed PsA by the end of the 2-year follow-up. In comparison, the researchers noted that “literature data on yearly incidence rates [of PsA] in different national cohorts indicate an incidence rate of approximately 4.3% per year.”
A total of 149 of the 196 patients with PsA confirmed by either clinical exam or MSUS were also positive on FOI, yielding a sensitivity of 76.0%. The specificity of FOI was 39.5%.
The sensitive visualization of musculoskeletal inflammation possible with FOI “may exceed its ability to detect clinically manifest PsA at high sensitivity or specificity, but early visualization is arguably of greater value as other imaging methods are currently available for detection of later stages of PsA,” the researchers wrote in their discussion. “A technique allowing early identification of PsA may be especially valuable for nonrheumatologists, including dermatologists and general practitioners, and help expedite more efficient referral to specialists.”
The findings were limited by several factors, including the nonrandomized design and small subgroup numbers, the researchers noted. Other limitations include the presence of alternative conditions such as osteoarthritis that might have complicated the imaging; the focus only on the hands; and potential variation in FOI assessment related to technical standards such as temperature and positioning.
However, the results support FOI as a safe and effective method of detecting early signs of joint inflammation that could predict increased risk for PsA in psoriasis patients, the researchers said.
The researchers added that more work is needed to evaluate FOI in clinical practice, but FOI has the potential to identify vascularization changes earlier than other imaging modalities and in advance of clinical symptoms.
“Accordingly, FOI may have the potential to improve patient outcomes in PsA by reducing the time to initiation of early treatment,” they concluded.
The study was supported by Fraunhofer ITMP, a nonprofit organization, and a research grant from Pfizer Germany. Some of the researchers disclosed financial relationships with many pharmaceutical companies, including Pfizer.