ABS0617 DEFINITIONS AND ONLINE RELIABILITY ASSESSMENT OF ELEMENTARY ULTRASOUND LESIONS IN TAKAYASU ARTERITIS: A STUDY FROM THE OMERACT LARGE VESSEL VASCULITIS ULTRASOUND WORKING GROUP

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Background: Instruments for monitoring disease activity in Takayasu arteritis (TAK) are needed for drug trials and clinical practice. Ultrasound (US) might be of value for this purpose. Following the development and validation of an US composite score for giant cell arteritis (OGUS), the large-vessel vasculitis-ultrasound subgroup (LVV-US) of the OMERACT Ultrasound Working Group is now developing an US score for TAK. A previous systematic literature review (SLR, unpublished ) identified the "macaroni sign", "stenosis", "occlusion", "aneurysm", "arterial wall calcification", "hyperperfusion of the arterial wall" as potential elementary US lesions. Here, we present the second step in the process of developing a new score, a Delphi and online reliability exercise. Objectives: (i) To agree upon new definitions for the key elementary US lesions in TAK; (ii) to test the inter-rater and intra-rater reliability of the new definitions through a structured web-based exercise. Methods: A Delphi questionnaire, informed by the SLR and international expert consensus, was distributed to 60 experts from the OMERACT LVV-US Working Group. The questionnaire included 12 statements on the relevance and definitions of elementary lesions, as well as 18 statements on the potential relevance of different anatomical segments for evaluation. The experts were asked to express their level of agreement with the proposed statements on a 1-5 Likert scale; consensus on acceptance was defined as ≥75% of participants voting with 4 or 5 for a given item. Subsequently, members of the OMERACT LVV-US Working Group were asked to submit anonymized representative US images of each selected TAK lesion and of healthy controls for a web-based reliability exercise. From all submissions, 150 images were finally selected by the steering group (100 from patients and 50 from healthy individuals), representing "macaroni sign" (n=65), "occlusion" (n=19), and "stenosis" (n=16). An electronic database was constructed using REDCap. A link to the web-based exercise was sent to the members of the OMERACT LVV-US Working Group, asking them to apply the definitions of the elementary lesions to each image. Two weeks later, participants re-evaluated the same, reordered, images to assess intra-rater reliability. Inter-rater and intra-rater reliability were calculated using the kappa coefficient (κ). Results: The Delphi consisted of three rounds. Participation was 71.7-78.3% (43-47/60 experts) across all rounds. A consensus was achieved for three key elementary lesions ("macaroni sign", "stenosis", "occlusion") for being included into the future US Score (Table 1). Other potential lesions ("aneurysm", "arterial wall calcification", "hyperperfusion of the arterial wall") were excluded. The group further agreed on including seven anatomical segments into the score: bilateral common carotid (CC), subclavian (SU) and axillary (AX) arteries and the abdominal aorta (AB). In the online reliability exercise, 45/60 (75.0%, 16 female) Working Group members participated in round 1. They reported a median of 10 years (interquartile range [IQR], 7-14) of experience with US in patients with LVV and to perform a median of 10 (IQR, 5-20) US scans per year in patients with TAK. Forty-four/45 participants (97.8%) participated in round 2. Overall, inter-rater reliability for the three elementary lesions was moderate to good in both rounds (Fleiss κ values ranging from 0.47–0.64, Table 2). Overall intra-rater reliability was good (mean Cohen's κ ranging from 0.72-0.79, Table 2). Conclusion: Definitions for key elementary US lesions in TAK were identified. The definitions demonstrated good overall inter- and intra-rater reliability in an online exercise. The next steps are the construction and validation of an US composite score for TAK. REFERENCES: NIL . Table 1Definitions of the ultrasound elementary lesions for Takayasu arteritis selected through the Delphi exerciseElementary lesionDefinitionMacaroni signHomogenous, usually hypo- to iso-echoic wall thickening, well delineated towards the luminal side, visible both in longitudinal and transverse planes, most commonly concentric in transverse scansStenosisUsually hypo- isoechoic vasculitic vessel wall thickening associated with characteristic Doppler curves showing turbulence (aliasing and/or persistent diastolic flow by color Doppler) and increased systolic and diastolic blood flow velocitiesOcclusionAbsence of color Doppler signals in a visible artery, filled with usually hypoechoic material even with low pulse repetition frequency and high color gain Table 2Fleiss κ for inter-rater reliability and Cohen's kappa for intra-rater reliability for elementary lesions.Fleiss κ for inter-rater reliabilityElementary lesionRound 1*Round 2*Macaroni sign0.64 (0.63-0.64)0.63 (0.63-0.64)Stenosis0.47 (0.47-0.48)0.55 (0.54-0.55)Occlusion0.58 (0.58-0.59)0.63 (0.62-0.63)Cohen's kappa for intra-rater reliabilityElementary lesionRound 1 - Round 2**Macaroni sign0.79 (0.09)Stenosis0.75 (0.17)Occlusion0.72 (0.18)*Data indicate the Fleiss k and 95% confidence interval in parenthesis; **Data indicate the mean of Cohen's kappa and standard deviation in parenthesis Acknowledgements: NIL . Disclosure of Interests: Alessandro Tomelleri Novartis, Fresenius-Kabi, Novartis, Simon Reider: None declared, Christian Dejaco AbbVie, Eli Lilly, Janssen, Novartis, Pfizer, Sparrow, Roche, Boehringer, Galapagos, Sanofi, AbbVie, Eli Lilly, Janssen, Novartis, Pfizer, Sparrow, Roche, Boehringer, Galapagos, Sanofi, AbbVie, Wolfgang Schmidt: None declared, Cristina Ponte Abbvie, GSK, Novartis, CSL Vifor, AstraZeneca, Abbvie, GSK, CSL Vifor, Roche, Alojzija Hocevar: None declared, Peter Mandl: None declared, Ana Filipa Águeda Amgen, ViforPharma, Fatma Alibaz- Oner: None declared, Simone Appenzeller: None declared, Markus Aschwanden: None declared, Hans Bastian: None declared, Philipp Bosch Johnson and Johnson, Novartis, Abbvie, Pfizer, Dario Camellino Astra-Zeneca, Boehringer Ingelheim, GSK, Janssen, Astra-Zeneca, Boehringer Ingelheim, GSK, Janssen, Vincent Casteleyn Bohringer Ingelheim, Abbvie, Novartis, UCB, Stavros Chrysidis: None declared, Thomas Daikeler Vifor, Abbvie, Abbvie, Novartis, Eugenio De Miguel Novartis, Abbvie, Pfizer, Janssen, Lilly, AbbVie, Novartis, Pfizer, MSD, BMS, UCB, Roche, Grunental, Janssen, Sanofi, Lylly, Abbvie, Novartis, Pfizer, Roche, Andreas Diamantopoulos: None declared, Georgios Filippou UCB pharma, UCB pharma, Abbvie, IBSA, UCB Pharma, Johnson & Johnson, IBSA, Eli Lilly, Ruchika Goel: None declared, Petra Hanova Eli Lilly, Fresenius Kabi, Wolfgang Hartung: None declared, Kei Ikeda Chugai Pharmaceutical, Chugai Pharmaceutical, Nevsun Inanc: None declared, Sandrine Jousse-Joulin: None declared, Aaron Juche: None declared, Rositsa Karalilova Abbvie, Pfizer, Novastis, Sandoz, Eli Lilly, UCB, Astra Zeneca, Johnson & Johnson, Kresten Keller: None declared, Søren Geill Kjær: None declared, Minna Kohler Setpoint Medical (research), Sonoma Therapeutics (research), Springer Publications (book royalties), Novartis (Medical advisory board - ended), J & J (Medical advisory board - ended), Matthew Koster Amgen, Pierluigi Macchioni: None declared, Sarah Mackie: None declared, Marcin Milchert: None declared, Durga Prasanna Misra: None declared, Juan Molina-Collada: None declared, Sara Monti: None declared, Daiki Nakagomi: None declared, Esperanza Naredo: None declared, Berit Dalsgaard Nielsen Abbvie, Speaker: Novartis. Consultant: Boehringer Ingelheim, Boehringer Ingelheim, Michihiro Ogasawara Chugai Pharmaceutical, Johannes Roth Novartis, Novo Nordisk, Valentin S. Schäfer AbbVie, Novartis, BMS, Chugai, Celgene, Medac, Sanofi, Lilly, Hexal, Pfizer, Janssen, Roche, Shire, Onkowissen, Royal College London, Boehringer-Ingelheim, UCB Fresenius, Alexion, Novartis, Chugai, AbbVie, Celgene, Sanofi, Lilly, Hexal, Pfizer, Amgen, BMS, Roche, Gilead, Medac, Boehringer-Ingelheim, Alexion, Novartis, Hexal, Lilly, Roche,

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