OP0142 THE IMPACT OF DISEASE EXTENT AND SEVERITY DETECTED BY QUANTITATIVE ULTRASOUND ANALYSIS IN THE DIAGNOSIS AND OUTCOME OF GIANT CELL ARTERITIS: RESULTS FROM THE TEMPORAL ARTERYBIOPSY VERSUS ULTRASOUND (TABUL) STUDY AND VALIDATION IN AN INDEPENDENT COHORT

Background Colour duplex sonography (CDS) is used in patients with giant cell arteritis (GCA) to detect inflammatory oedema of the vascular wall, known as “halo”. A quantitative analysis of halo characteristics to grade the severity and extension of vascular involvement detected by CDS could improve GCA assessment. Objectives To develop a quantitative CDS score to improve the diagnosis of GCA, and to correlate the score with histologic findings and clinical outcome. To determine the additional role of clinical signs/symptoms to the CDS score. Methods We selected patients with a positive CDS and a diagnosis of GCA recruited into the Temporal Artery (TA) Biopsy (TAB) vs Ultrasound in Diagnosis of GCA (TABUL) study. Due to collinearity we fitted 4 different CDS models including combinations of the following items: number of sites and distribution of halos, average and maximum intima-media thickness (IMT) at the level of the TA and axillary arteries (AX) and halos bilaterality. We fitted 4 models with clinical and laboratory findings. We combined the best CDS and clinical models (according to the Akaike Information Criterium) to identify independent correlates of a TAB diagnostic for GCA and of clinical outcome at 6 months (visual loss + VDI ocular + glucocorticoids > 10 mg/day and/or need for immunosuppressants) and performed a 10-fold cross-validation of the model. We validated the clinical outcome model on an independent cohort referred to the fast-track ultrasound clinics of two European rheumatology centres. Results We included 135 patients with GCA from TABUL (female: 68%, age 73±8) and 72 patients from an independent cohort (female: 46%, age 75±7). The best fitting CDS model for TAB used maximum IMT size and bilaterality of halos at the level of the TA and AX. The best fitting clinical model included raised ESR/CRP, polymyalgia rheumatica, headache and ischaemic symptoms (jaw/tongue claudication, amaurosis, double vision, stroke). The coefficients from the combined models (CDS and clinical) allowed to produce a comprehensive score (GCA-US score) to stratify patients according to the probability of having a positive TAB (Figure 1). Model discrimination was fair (AUC-ROC 0.77, 95%CI 0.68-0.84). None of the considered variables was associated with clinical outcome expressing worse prognosis at 6 months. Conclusion We demonstrated that a quantitative analysis of CDS findings adds important diagnostic information with a computable estimate of the probability of positive histology, supporting the use of CDS as a surrogate diagnostic tool to replace TAB. A few CDS and clinical findings can be combined into a simple computable risk score to support a diagnosis of GCA. Disclosure of Interests Sara Monti: None declared, Cristina Ponte Speakers bureau: Roche, Claudio Pereira: None declared, Federica Rumi: None declared, Greta Carrara: None declared, Catherine Klersy: None declared, Andrew Hutchings: None declared, Wolfgang A. Schmidt: None declared, Bhaskar Dasgupta Consultant for: Roche, GSK, Sanofi, BMS, Abbvie, Speakers bureau: Roche, Roberto Caporali Speakers bureau: AbbVie, Bristol-Myers Squibb, Celgene, Roche, Genzyme, Lilly, MSD, Pfizer, UCB, Carlomaurizio Montecucco Speakers bureau: AbbVie, Bristol-Myers Squibb, Celgene, Sanofi, Genzyme, Lilly, MSD, Pfizer, UCB, Raashid Luqmani Grant/research support from: Roche, Vifor and GSK