THU0537 VALIDITY AND DIAGNOSTIC PERFORMANCE OF FLUORESCENCE OPTICAL IMAGING MEASURING SYNOVITIS IN HAND OSTEOARTHRITIS. RESULTS FROM THE NOR-HAND STUDY.
Authors: Ø. Maugesten, A. Mathiessen, H. B. Hammer, T. K. Kvien, S. V. Hestetun, T. Uhlig, S. Ohrndorf, I. K. Haugen
Journal: Annals of the Rheumatic Diseases (2020)

Background: Fluorescence Optical Imaging (FOI) demonstrates enhanced microcirculation in finger joints as a sign of inflammation. Objectives: We wanted to assess the validity and diagnostic performance of FOI measuring synovitis, comparing it with Magnetic Resonance Imaging (MRI)- and ultrasound-detected synovitis in persons with hand osteoarthritis (OA). Methods: Two hundred and twenty-one participants (88% female, age (SD) 60.6 (6.2) years) with hand OA from the Nor-Hand study underwent FOI and grey scale (GS) and power Doppler (PD) ultrasound of the bilateral hands and contrast-enhanced MRI of the dominant hand. The FOI scan was performed after the administration of an intravenous fluorescence dye (indocyanine green, ICG) and 360 images (1/second) were produced in 6 minutes. One reader scored the bilateral distal interphalangeal (DIP), proximal interphalangeal (PIP), metacarpophalangeal (MCP) and first carpometacarpal (CMC-1) joints for FOI enhancement, blinded for clinical information and other imaging data. Images were scored according to the ‘FOI activity score’ (FOIAS) where four out of 360 images are assessed, defined as phase 1, 2, and 3, based on the inflow and washing out of the fluorescence dye, and a composite image (Prima Vista Mode; PVM) of the 240 first images. Two readers evaluated separately the severity of MRI-defined synovitis (grade 0-3) in the DIP, PIP, MCP and CMC-1 joints of the dominant hand and the severity of GS synovitis (grade 0-3) and PD activity (grade 0-3) in the same joints of the hands bilaterally. Spearman’s rho was calculated for correlations between sum scores of all joints for FOI, MRI and ultrasound and sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV) and area under the curve (AUC) for FOI using MRI and ultrasound as reference. Results: Despite frequent MRI and ultrasound findings in the CMC-1 joint, no FOI enhancement was detected in the thumb base, and CMC-1 was excluded from the analyses. FOI had poor to fair correlations with MRI and GS synovitis and PD activity. The strongest correlation with MRI was found for PVM in the PIP joints with Spearman’s rho of 0.32, while the DIP joints had consistently the weakest correlations ranging from 0 to 0.14 (Figure 1). None of the FOI phases or PVM demonstrated both good sensitivity and specificity, and AUC remained low with both MRI and GS synovitis as a reference (table 1). The NPVs of FOI were consistently higher when GS synovitis was used as reference rather than MRI, due to higher frequency of low degree MRI-defined synovitis. However, when changing cut-off for MRI synovitis as reference from grade 1 to grade 2 the diagnostic performance of FOI increased to the level of GS synovitis. The diagnostic performance for FOI was similar with both GS synovitis and PD activity as reference. Table 1. Diagnostic performance of FOI measuring synovitis in hand OA using MRI and GS synovitis as reference FOI Reference Sensitivity Specifisity PPV NPV AUC PVM MRI 0.48 0.72 0.61 0.61 0.61 Phase 1 0.02 0.99 0.61 0.53 0.50 Phase 2 0.58 0.62 0.58 0.62 0.60 Phase 3 0.24 0.90 0.67 0.57 0.57 PVM GS 0.59 0.64 0.17 0.93 0.62 Phase 1 0.02 0.99 0.28 0.89 0.51 Phase 2 0.69 0.56 0.17 0.94 0.63 Phase 3 0.23 0.86 0.17 0.90 0.56 FOI; Fluorescence optical imaging, PVM; Prima Vista Mode, GS; Grey scale, PVM; Prima Vista Mode, PPV; Positive Predictive Value, NPV; Negative Predictive Value, AUC; Area under the curve Conclusion: FOI sum scores showed poor to fair correlations with MRI- and ultrasound-detected synovitis in persons with hand OA. These findings might be explained by the low-grade inflammation with minor vascularization in the majority of inflamed joints. None of the FOI phases or PVM demonstrated both good sensitivity and specificity and the method was not able to detect CMC-1 synovitis. Disclosure of Interests: Øystein Maugesten: None declared, Alexander Mathiessen: None declared, Hilde Berner Hammer Consultant of: Has received fees as consultant from Roche, AbbVie and Novartis., Speakers bureau: Has received fees for speaking from AbbVie, BMS, Pfizer, UCB, Roche, MSD and Novartis, Tore K. Kvien Grant/research support from: Received grants from Abbvie, Hospira/Pfizer, MSD and Roche (not relevant for this abstract)., Consultant of: Have received personal fees from Abbvie, Biogen, BMS, Celltrion, Eli Lily, Hospira/Pfizer, MSD, Novartis, Orion Pharma, Roche, Sandoz, UCB, Sanofi and Mylan (not relevant for this abstract)., Paid instructor for: Have received personal fees from Abbvie, Biogen, BMS, Celltrion, Eli Lily, Hospira/Pfizer, MSD, Novartis, Orion Pharma, Roche, Sandoz, UCB, Sanofi and Mylan (not relevant for this abstract)., Speakers bureau: Have received personal fees from Abbvie, Biogen, BMS, Celltrion, Eli Lily, Hospira/Pfizer, MSD, Novartis, Orion Pharma, Roche, Sandoz, UCB, Sanofi and Mylan (not relevant for this abstract)., Sigrid Valen Hestetun: None declared, Till Uhlig: None declared, Sarah Ohrndorf: None declared, Ida K. Haugen: None declared