Background ICG-enhanced fluorescence optical imaging (FOI) is a novel technology for the assessment of inflammation in arthritis [1,2]. Previous studies were mainly focused on articular findings. Extraarticular changes have not yet been studied systematically.
Objectives This is the first report of extraarticular FOI patterns in a large cohort of subjects with psoriatic arthritis (PsA).
Methods 201 FOI sequences in 172 patients with PsA (59% females, mean age 54,1 years, mean disease duration 5,8 years (median 3,1 years, range 2 weeks – 42,7 years), mean DAS28 3,0) were selected from our FOI registry. FOI was performed according to the standard procedure [1,2]. 36 regions (both hands: nail, nail fold, middle phalanx of D 2-5, proximal phalanx of D 1-5, metacarpal area) were read for the sum image (PVM) and the phases P1 and P2 . Different FOI patterns were identified, characterized and classified by the method of categorical morphological analysis. 30 subjects with seropositive, anti-CCP-positive rheumatoid arthritis (mean disease duration 4,6 years, median 1,9 years, mean DAS28 3,5) served as control.
Results 16 distinct extraarticular FOI patterns could be identified in subjects with PsA in the following areas. (A) Nail: Cold Nail, Green Nail, Hot Nail, Caldera, Half Moon. (B) Nail fold: Werner's sign , Bishop's crook. (C) Phalanges: Hourglass, Pyramid, Caterpillar, Barrel, Stripe, Thread. (D) Metacarpal area: Island, Archipelago, Geographic Map. Nail fold changes were the most common finding (72% of sequences), followed by stripe (58%), hourglass (32%), pyramid (30%), barrel (28%) and thread (28%). Patterns in area A-C were mainly seen in PVM and P2, patterns in area D almost exclusively in P1. 66 subjects did not have any clinical signs in the region of the hands (no swollen or tender joints). At least one extraarticular pattern was present in all of those subjects. Hourglass patterns were more frequent in PsA comparing to RA (32% vs 7%). Archipelago patterns (group of small islands) were observed exclusively in subjects with PsA. Areas of reduced perfusion and deviations from the typical course of the phases were seen in 19% of PsA sequences vs 3% in RA.
Conclusions Extraarticular FOI findings were common in PsA. The classification of their morphologies in PsA enables a standardized assessment of FOI sequences beyond the quantitative fluorescence optical imaging score FOIAS [1,2]. Some patterns may be characteristic for PsA and could have a diagnostic value. Extraarticular signal intensities in the hands of patients with clinically asymptomatic hand and finger joints probably represent subclinical disease activity. This observation could play a role in early diagnosis and in the assessment of therapeutic response.
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Werner SG, Langer HE, Schott P, et al: Indocyanine Green–Enhanced Fluorescence Optical Imaging in Patients With Early and Very Early Arthritis: A Comparative Study With Magnetic Resonance Imaging. Arthritis Rheum 2013; 65(12):3036–3044
Acknowledgements The research was supported in part by a research grant of Pfizer Pharma GmbH Germany
Disclosure of Interest None declared