ASSESSMENT OF INTERREADER RELIABILITY IN SCORING PATIENTS WITH HAND OSTEOARTHRITIS AND PSORIATIC ARTHRITIS BY FLUORESCENCE OPTICAL IMAGING

Background: Fluorescence Optical Imaging (FOI) utilises the fluorophore indocyanine green (ICG) to reflect enhanced microcirculation in hand and finger joints due to inflammation. Objectives: We wanted to assess the interreader reliability of FOI enhancement in patients with hand osteoarthritis (OA) and psoriatic arthritis (PsA). Furthermore, predefined typical morphologic patterns were included to determine the ability of FOI to discriminate between both diagnoses. Methods: An atlas with example images of grade 0-3 in different joint groups and typical morphologic patterns (‘streaky signals’[1], ‘green/blue nail sign’[2], ‘Werner sign’[3,4], and ‘Bishop’s crozier sign’) of PsA and hand OA was created. Two readers scored all joints in both hands (30 in total) of 20 cases with hand OA and PsA. The cases were randomly mixed and both readers were blinded to diagnosis. Each joint was rated on a semiquantitative scale from 0 to 3 in five different images (PrimaVista Mode (PVM), phase 1, 2 (first and middle image), and 3) during the FOI sequence according to the scoring method FOIAS (fluorescence optical imaging activity score)[1,3]. Interreader reliability on scoring joint enhancement was calculated using linear weighted Cohen’s kappa (κ). Agreement on diagnosis (hand OA vs. PsA) and different morphologic patterns was assessed by calculating (regular) Cohen’s kappa. Results: Overall agreement on scoring joint enhancement (all phases) was substantial (κ = 0.75), with greatest consensus in phase 2 first (κ = 0.75) and lowest agreement in phase 1 (κ = 0.46). Reliability varied in different joint groups (wrist, MCP, (P)IP, DIP), with almost perfect overall agreement on PIP joint affection (κ = 0.81), substantial agreement on wrist (κ = 0.69) and DIP joint affection (κ = 0.63), and moderate agreement on MCP joint affection (κ = 0.49) across all phases. Consensus on morphologic patterns showed overall fair agreement (κ = 0.37) with a similar kappa value on the ability to discriminate between both diagnoses (κ = 0.3). Conclusion: Joint enhancement in FOI can be reliably assessed using a predefined scoring method. The ability of FOI to differentiate between hand OA and PsA seems to be limited. Clearer definition and more training might be needed to better agree on morphologic patterns in FOI. REFERENCES: [1] Glimm AM, Werner SG, Burmester GR, et al. Ann Rheum Dis. 2016 Mar;75(3):566-570 [2] Wiemann O, Werner SG, Langer HE, et al. J Dtsch Dermatol Ges. 2019 Feb;17(2):138-148 [3] Werner SG, Langer HE, Ohrndorf S, et al. Ann Rheum Dis. 2012 Apr;71(4):504-510 [4] Zeidler H 2019. Fluoreszenzoptische Bildgebung. In: Zeidler H, Michel BA. Differenzialdiagnose rheumatischer Erkrankungen 5. Aufl. Springer, Heidelberg, S. 88-89 Disclosure of Interests: Benedict Drude: None declared, Øystein Maugesten: None declared, Stephanie Gabriele Werner: None declared, Gerd Rüdiger Burmester: None declared, Jörn Berger Employee of: Xiralite GmbH, Ida K. Haugen: None declared, Sarah Ohrndorf: None declared Citation: Ann Rheum Dis, volume 80, supplement 1, year 2021, page 983Session: Diagnostics and imaging procedures (POSTERS only)