Magnetic resonance imaging to monitor disease activity in giant cell arteritis treated with ultra-short glucocorticoids and tocilizumab.

OBJECTIVES: MRI is well established for diagnosing GCA. Its role in monitoring disease activity has yet to be determined. We investigated vascular and musculoskeletal inflammation using MRI in the patients of the GUSTO trial to assess the utility of MRI in monitoring disease activity. METHODS: Eighteen patients with newly diagnosed GCA received 500 mg methylprednisolone intravenously for 3 consecutive days followed by tocilizumab monotherapy from day 3 until week 52. Cranial, thoracic and abdominal MRI exams were performed at baseline (active, new-onset disease), and at weeks 24, 52 (remission on-treatment), and 104 (remission off-treatment). MRI findings typical for PMR as well as extent and severity of vasculitic disease were rated. RESULTS: In total, 673 vascular segments and 943 musculoskeletal regions in 55 thoracic/abdominal MRI and 490 vascular segments in 49 cranial MRI scans of 18 patients were analysed. Vasculitic vessels were still detectable in one in four cranial segments at week 24. At weeks 52 and 104, no cranial vascular segment showed a vasculitic manifestation. Large vessels, except for the ascending aorta, and PMR displayed little or no decrease in inflammatory findings over time. CONCLUSION: Vasculitic manifestations in the cranial vessels normalised after 52 weeks of treatment, whereas large vessel and PMR findings persisted despite lasting full remission. The dynamics of cranial vessel signals suggest that MRI of these arteries might qualify as a potential diagnostic tool for monitoring disease activity and for detecting relapse after 52 weeks of treatment.

Musculoskeletal magnetic resonance imaging findings support a common spectrum of giant cell arteritis and polymyalgia rheumatica.

OBJECTIVES: To investigate the proportion and distribution of contrast enhancement (CE) of musculoskeletal structures with MRI of the thorax/abdomen/pelvis in giant cell arteritis (GCA). METHODS: CE at 34 musculoskeletal sites was rated with a 4-point ordinal scale. Patients were divided into groups with/without glucocorticoid (GC) treatment and with/without symptoms of polymyalgia rheumatica (PMR). Two composite scores were created: an MRI-score, including seven sites and a Limited-MRI-score, including four sites. RESULTS: Retrospectively, 90 consecutive patients with GCA were included. The population included 54 and 36 patients with and without PMR symptoms, respectively, and 45 (50%) patients were receiving GCs at the time of MRI. CE was found in 90.7% of lumbar spines, 87.5% of the pelvis, 82.2% of shoulder girdles and in 95.6% at any site in patients without GCs. The proportion of patients without and with GCs with at least moderate enhancement was 91.1%/75.6% at ≥ 1-3, 75.6%/51.1% at ≥ 4-6 and 64.4%/28.9% at ≥ 7-9 sites. The mean difference between the proportion of pathological CE in patients with and without GCs was 27.4% for synovial sites and 18.3% for periarticular/musculotendinous sites. Both composite scores captured substantial differences between groups, correlation was very strong between scores. CONCLUSIONS: MRI shows CE of musculoskeletal structures typical of PMR in most patients with GCA, supporting the concept of "GCA-PMR Spectrum Disease". Changes are more frequent at periarticular/musculotendinous sites and in the presence of PMR symptoms. A clear response to GCs is evident, less so for periarticular/musculotendinous sites.

EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice: 2023 update.

OBJECTIVES: To update the EULAR recommendations for the use of imaging modalities in primary large vessel vasculitis (LVV). METHODS: A systematic literature review update was performed to retrieve new evidence on ultrasound, MRI, CT and [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) for diagnosis, monitoring and outcome prediction in LVV. The task force consisted of 24 physicians, health professionals and patients from 14 countries. The recommendations were updated based on evidence and expert opinion, iterating until voting indicated consensus. The level of agreement was determined by anonymous votes. RESULTS: Three overarching principles and eight recommendations were agreed. Compared to the 2018 version, ultrasound is now recommended as first-line imaging test in all patients with suspected giant cell arteritis, and axillary arteries should be included in the standard examination. As an alternative to ultrasound, cranial and extracranial arteries can be examined by FDG-PET or MRI. For Takayasu arteritis, MRI is the preferred imaging modality; FDG-PET, CT or ultrasound are alternatives. Although imaging is not routinely recommended for follow-up, ultrasound, FDG-PET or MRI may be used for assessing vessel abnormalities in LVV patients with suspected relapse, particularly when laboratory markers of inflammation are unreliable. MR-angiography, CT-angiography or ultrasound may be used for long-term monitoring of structural damage, particularly at sites of preceding vascular inflammation. CONCLUSIONS: The 2023 EULAR recommendations provide up-to-date guidance for the role of imaging in the diagnosis and assessment of patients with LVV.

The provisional OMERACT ultrasonography score for giant cell arteritis.

OBJECTIVES: To develop an Outcome Measures in Rheumatology (OMERACT) ultrasonography score for monitoring disease activity in giant cell arteritis (GCA) and evaluate its metric properties. METHODS: The OMERACT Instrument Selection Algorithm was followed. Forty-nine members of the OMERACT ultrasonography large vessel vasculitis working group were invited to seven Delphi rounds. An online reliability exercise was conducted using images of bilateral common temporal arteries, parietal and frontal branches as well as axillary arteries from 16 patients with GCA and 7 controls. Sensitivity to change and convergent construct validity were tested using data from a prospective cohort of patients with new GCA in which ultrasound-based intima-media thickness (IMT) measurements were conducted at weeks 1, 3, 6, 12 and 24. RESULTS: Agreement was obtained (92.7%) for the OMERACT GCA Ultrasonography Score (OGUS), calculated as follows: sum of IMT measured in every segment divided by the rounded cut-off values of IMTs in each segment. The resulting value is then divided by the number of segments available. Thirty-five members conducted the reliability exercise, the interrater intraclass correlation coefficient (ICC) for the OGUS was 0.72-0.84 and the median intrareader ICC was 0.91. The prospective cohort consisted of 52 patients. Sensitivity to change between baseline and each follow-up visit up to week 24 yielded standardised mean differences from -1.19 to -2.16, corresponding to large and very large magnitudes of change, respectively. OGUS correlated moderately with erythrocyte sedimentation rate, C reactive protein and Birmingham Vasculitis Activity Score (corrcoeff 0.37-0.48). CONCLUSION: We developed a provisional OGUS for potential use in clinical trials.

Diffusion-weighted magnetic resonance imaging for the diagnosis of giant cell arteritis - a comparison with T1-weighted black-blood imaging.

OBJECTIVES: To investigate the diagnostic performance of diffusion-weighted imaging (DWI) of the superficial cranial arteries in the diagnosis of giant cell arteritis (GCA). METHODS: Retrospectively, 156 patients with clinically suspected GCA were included. A new 4-point ordinal DWI rating scale was developed. A post-contrast, fat-suppressed, T1-weighted "black-blood" sequence (T1-BB) was rated for comparison. Ten arterial segments were assessed: common superficial temporal arteries, temporal and parietal branches, occipital and posterior auricular arteries bilaterally. The expert clinical diagnosis after ≥ 6 months of follow-up was the diagnostic reference standard. Diagnostic accuracy was evaluated for different rating methods. RESULTS: The study cohort consisted of 87 patients with and 69 without GCA. For DWI, the area under the curve was 0.90. For a cut-off of ≥ 2 consecutive pathological slices, DWI showed a sensitivity of 75.9%, a specificity of 94.2% and a positive likelihood ratio of 13.09. With a cut-off of ≥ 3 consecutive pathological slices, sensitivity was 70.1%, specificity was 98.6%, and the positive likelihood ratio was 48.38. For the T1-BB, values were 88.5%, 88.4% and 7.63, respectively. The inter-rater analysis for DWI with a cut-off of ≥ 2 pathological slices showed a kappa of 1.00 on the patient level and 0.85 on the arterial segment level. For the T1-BB the kappa was 0.78 and 0.79, respectively. CONCLUSION: DWI of the superficial cranial arteries demonstrates a good diagnostic accuracy and reliability for the diagnosis of GCA. DWI is widely available and can be used immediately in clinical practice for patients with suspected GCA.

Spectrum of Large and Medium Vessel Vasculitis in Adults: Primary Vasculitides, Arthritides, Connective Tissue, and Fibroinflammatory Diseases.

PURPOSE OF REVIEW: To provide a comprehensive overview of the spectrum of large and medium vessel vasculitis in adults with primary vasculitides, arthritides, connective tissue, and fibroinflammatory diseases as well as vasculitis mimics, for an efficient differential diagnosis and initial diagnostic approach. RECENT FINDINGS: Imaging has had a tremendous impact on the diagnosis of medium to large vessel vasculitis, now often replacing histopathologic confirmation and identifying new disease manifestations (e.g., intracranial disease in giant cell arteritis; vascular manifestations of IgG4-related disease). Novel diseases or syndromes involving blood vessels have been described (e.g., VEXAS-Syndrome with polychondritis). The use of the terms "medium" or "large" vessel varies considerably between medical specialties. The differential diagnosis of large and medium vessel vasculitis is becoming increasingly complex as new entities or disease manifestations of known inflammatory rheumatic diseases are regularly identified. A more precise and widely recognized definition of the vessel sizes would make future research more comparable.

Spectrum of Large- and Medium-Vessel Vasculitis in Adults: Neoplastic, Infectious, Drug-Induced, Autoinflammatory, and Primary Immunodeficiency Diseases.

PURPOSE OF REVIEW: To provide a comprehensive review of drugs and neoplastic, infectious, autoinflammatory, and immunodeficiency diseases causing medium- to large-vessel vasculitis in adults with emphasis on information essential for the initial diagnostic process. RECENT FINDINGS: Entities with medium- to large-vessel vasculitis as clinical manifestations have been described recently (e.g., adenosine deaminase-2 deficiency, VEXAS-Syndrome), and vasculitis in established autoinflammatory or immunodeficiency diseases is increasingly being identified. In the diagnostic process of medium- to large-vessel vasculitis in adults, a large variety of rare diseases should be included in the differential diagnosis, especially if diagnosis is made without histologic confirmation and in younger patients. Although these disorders should be considered, they will undoubtedly remain rare in daily practice.

Quantitative ultrasound to monitor the vascular response to tocilizumab in giant cell arteritis.

OBJECTIVES: To characterize the effect of ultra-short glucocorticoids followed by Tocilizumab monotherapy on the intima-media thickness (IMT) in GCA. METHODS: Eighteen GCA patients received 500 mg for 3 consecutive days (total of 1500mg) i.v. methylprednisolone on days 0-2, followed by i.v. Tocilizumab (8 mg/kg) on day 3 and thereafter weekly s.c. Tocilizumab injections (162 mg) over 52 weeks. US of temporal (TAs), axillary (AAs) and subclavian (SAs) arteries was performed at baseline, on days 2-3, and at weeks 4, 8, 12, 24 and 52. The largest IMT of all segments and IMT at landmarks of AA/SA were recorded. IMT was scaled by mean normal values and averaged. Each segment was classified according to diagnostic cut-offs. RESULTS: Of the 18 GCA patients, 16 patients had TA and 6 had extracranial large artery involvement. The IMT showed a sharp decline on day 2/3 in the TAs and AAs/SAs. In TAs, this was followed by an increase to baseline levels at week 4 and a subsequent slow decrease, which was paralleled by decreasing symptoms and achievement of clinical remission. The AAs/SAs showed a new signal of vasculitis at week 4 in three patients, with an IMT increase up to week 8. CONCLUSION: Glucocorticoid pulse therapy induced a transient decrease of the IMT in TAs and AAs/SAs. Tocilizumab monotherapy resulted in a slow and steady decrease in IMT of the TAs and a smaller and delayed effect on the AAs/SAs. The data strongly support a remission-inducing effect of Tocilizumab and argue the case for US having an important role in monitoring disease activity in GCA. TRIAL REGISTRATION: ClinicalTrials.gov, www.clinicaltrials.gov, NCT03745586.

DWI scrolling artery sign for the diagnosis of giant cell arteritis: a pattern recognition approach.

OBJECTIVES: To investigate the diagnostic accuracy of a pattern recognition approach for the evaluation of MRI scans of the head with diffusion-weighted imaging (DWI) in suspected giant cell arteritis (GCA). METHODS: Retrospectively, 156 patients with suspected GCA were included. The 'DWI-Scrolling-Artery-Sign' (DSAS) was defined as hyperintense DWI signals in the cranial subcutaneous tissue that gives the impression of a blood vessel when scrolling through a stack of images. The DSAS was rated by experts and a novice in four regions (frontotemporal and occipital, bilaterally). The temporal, occipital and posterior auricular arteries were assessed in the T1-weighted black-blood sequence (T1-BB). The diagnostic reference was the clinical diagnosis after ≥6 months of follow-up. RESULTS: The population consisted of 87 patients with and 69 without GCA; median age was 71 years and 59% were women. The DSAS showed a sensitivity of 73.6% and specificity of 94.2% (experts) and 59.8% and 95.7% (novice), respectively. Agreement between DSAS and T1-BB was 80% for the region level (499/624; kappa(κ)=0.59) and 86.5% for the patient level (135/156; κ=0.73). Inter-reader agreement was 95% (19/20; κ=0.90) for DSAS on the patient level and 91.3% (73/80; κ=0.81) on the region level for experts. For expert versus novice, inter-reader agreement for DSAS was 87.8% on the patient level (137/156; κ=0.75) and 91.2% on the region level (569/624; κ=0.77). CONCLUSIONS: The DSAS can be assessed in less than 1 min and has a good diagnostic accuracy and reliability for the diagnosis of GCA. The DSAS can be used immediately in clinical practice.

Ultrasound intima-media thickness cut-off values for the diagnosis of giant cell arteritis using a dual clinical and MRI reference standard and cardiovascular risk stratification.

Objectives: To derive segmental cut-off values and measures of diagnostic accuracy for the intima-media thickness of compressed temporal artery segments for the diagnosis of giant cell arteritis (GCA) on the patient level. To examine the influence of cardiovascular risk. Methods: Retrospectively, patients evaluated for GCA with an ultrasound of the temporal arteries and an MRI of the head, including a T1-fatsat-black blood (T1-BB) sequence, were identified and classified based on cardiovascular risk and a dual reference standard of T1-BB on the segmental level and the clinical diagnosis on the patient level. Intima-media thickness of the common superficial temporal artery (CSTA), frontal and parietal branches (FB, PB) were measured by compression technique. Statistically and clinically optimal (specificity of approx. 90% for the patient level) cut-offs were derived. Diagnostic accuracy was evaluated on the patient level. Results: The population consisted of 144 patients, 74 (51.4%) with and 70 (48.6%) without GCA. The statistically optimal cut-offs were 0.86 mm, 0.68 mm and 0.67 mm for the CSTA, the FB and PB, respectively. On the patient level sensitivity and specificity were 86.5 and 81.4%. Clinically optimal cut-offs were 1.01 mm, 0.82 mm and 0.69 mm and showed a sensitivity of 79.7% and a specificity of 90.0%. For patients without high cardiovascular risk, statistically optimal cut-offs showed a sensitivity of 89.6% and a specificity of 90.5%. Conclusion: Newly derived ultrasound intima-media thickness cut-offs with a dual reference standard show high diagnostic accuracy on the patient level for the diagnosis of GCA, particularly in patients without high cardiovascular risk.

Cluster analysis of flowcytometric immunophenotyping with extended T cell subsets in suspected immunodeficiency.

BACKGROUND: Patients with immunodeficiencies commonly experience diagnostic delays resulting in morbidity. There is an unmet need to identify patients earlier, especially those with high risk for complications. Compared to immunoglobulin quantification and flowcytometric B cell subset analysis, expanded T cell subset analysis is rarely performed in the initial evaluation of patients with suspected immunodeficiency. The simultaneous interpretation of multiple immune variables, including lymphocyte subsets, is challenging. OBJECTIVE: To evaluate the diagnostic value of cluster analyses of immune variables in patients with suspected immunodeficiency. METHODS: Retrospective analysis of 38 immune system variables, including seven B cell and sixteen T cell subpopulations, in 107 adult patients (73 with immunodeficiency, 34 without) evaluated at a tertiary outpatient immunology clinic. Correlation analyses of individual variables, k-means cluster analysis with evaluation of the classification into "no immunodeficiency" versus "immunodeficiency" and visual analyses of hierarchical heatmaps were performed. RESULTS: Binary classification of patients into groups with and without immunodeficiency was correct in 54% of cases with the full data set and increased to 69% and 75% of cases, respectively, when only 16 variables with moderate (p < .05) or 7 variables with strong evidence (p < .01) for a difference between groups were included. In a cluster heatmap with all patients but only moderately differing variables and a heatmap with only immunodeficient patients restricted to T cell variables alone, segregation of most patients with common variable immunodeficiency and combined immunodeficiency was observed. CONCLUSION: Cluster analyses of immune variables, including detailed lymphocyte flowcytometry with T cell subpopulations, may support clinical decision making for suspected immunodeficiency in daily practice.

Management of giant-cell arteritis in Switzerland: an online national survey.

AIMS OF THE STUDY: To assess current practices in diagnosing, treating, and following-up giant-cell arteritis by specialists in Switzerland and to identify the main barriers to using diagnostic tools. METHODS: We performed a national survey of specialists potentially caring for patients with giant-cell arteritis. The survey was sent by email to all members of the Swiss Societies of Rheumatology and for Allergy and Immunology. A reminder was sent to nonresponders after 4 and 12 weeks. Its questions covered the following dimensions: respondents' main characteristics, diagnosis, treatment, and imaging's role during follow-up. The main study results were summarized using descriptive statistics. RESULTS: Ninety-one specialists, primarily aged 46-65 years (n = 53/89; 59%), working in academic or nonacademic hospitals or private practice, and treating a median of 7.5 (interquartile range [IQR]: 3-12) patients with giant-cell arteritis per year participated in this survey. Ultrasound of temporal arteries/large vessels (n = 75/90; 83%) and positron-emission-tomography-computed tomography (n = 52/91; 57%) or magnetic resonance imaging (n = 46/90; 51%) of the aorta/extracranial arteries were the most common techniques used to diagnose giant-cell arteritis with cranial or large vessel involvement, respectively. Most participants reported a short time to obtain imaging tests or arterial biopsy. The glucocorticoid tapering scheme, glucocorticoid-sparing agent, and glucocorticoid-sparing treatment duration varied among the participants. Most physicians did not follow a predefined repeat imaging scheme for follow-up and mainly relied on structural changes (vascular thickening, stenosis, or dilatation) to drive treatment choice. CONCLUSIONS: This survey indicates that imaging and temporal biopsy are rapidly accessible for diagnosing giant-cell arteritis in Switzerland but highlights heterogeneous practice in many disease management areas.

Vision loss in patients with giant cell arteritis treated with tocilizumab.

OBJECTIVES: Giant cell arteritis (GCA) may lead to vision loss. To what extent tocilizumab (TCZ) is able to prevent vision loss is unknown. The aim was to analyze the occurrence of vision loss in a large GCA cohort treated with TCZ. METHODS: In this observational monocentric study, GCA patients treated with TCZ between the years 2010 and 2018 were studied. Demographic, clinical, and laboratory data were analyzed. RESULTS: A total of 186 patients were included (62% female); 109 (59%) fulfilled the American College of Rheumatology (ACR) criteria, in 123 (66%) patients, large vessel vasculitis was diagnosed by magnetic resonance-angiography (MRA). Cumulative duration of TCZ treatment was 224 years, median treatment duration was 11.1 (IQR 5.6-17.9) months. Glucocorticoids (GC) were tapered over a median of 5.8 (IQR 3.0-8.5) months. At baseline, visual symptoms were present in 70 (38%) and vision loss in 21 (11%) patients. Patients with vision loss at baseline were older (p = 0.032), had a lower C-reactive protein (p = 0.002), and showed a negative association with MRA of the aorta (p = 0.006). Two patients (1.1%) developed vision loss, both at the initiation of TCZ treatment. CONCLUSION: Our data show a very low incidence of vision loss in TCZ-treated patient. The two cases of AION occurred at the initiation of therapy, they support the hypothesis that advanced, and established structural changes of arteries are key factors for this accident. Whether a shorter duration of concomitant GC treatment is risky regarding vision loss needs to be studied.

Case Report: Genetic Double Strike: VEXAS and TET2-Positive Myelodysplastic Syndrome in a Patient With Long-Standing Refractory Autoinflammatory Disease.

Somatic genetic mutations involving the innate and inflammasome signaling are key drivers of the pathogenesis of myelodysplastic syndromes (MDS). Herein, we present a patient, who suffered from a long-standing refractory adult-onset autoinflammatory syndrome (AIS), previously interpreted as various distinct rheumatic disorders. Developing pancytopenia and particularly macrocytic anemia prompted the screening for a hematological malignancy, which led to the diagnosis of a TET-2-positive MDS. The impressive and continuously changing range of organ involvement, with remarkable refractoriness to anti-inflammatory treatment, exceeded the common autoinflammatory phenotype of MDS patients. This prompted us to suspect a recently discovered disease, characterized by somatic mutations of the UBA1 gene: the VEXAS (Vacuoles, E1 enzyme, X-linked, Autoinflammatory, Somatic) syndrome, which was ultimately confirmed by genetic testing. Reevaluation of previous bone marrow biopsies showed the presence of characteristic vacuoles in myeloid- and erythroid progenitor cells. Our case illustrates that the triad of an unresponsive multisystemic autoinflammatory disease, hematological abnormalities and vacuoles in myeloid- and erythroid progenitors in the bone marrow biopsy should prompt screening for the VEXAS syndrome.

Tocilizumab monotherapy after ultra-short glucocorticoid administration in giant cell arteritis: a single-arm, open-label, proof-of-concept study.

BACKGROUND: Two randomised controlled trials showed a glucocorticoid-sparing effect of tocilizumab in patients with giant cell arteritis. In the GUSTO trial we aimed to evaluate the efficacy and safety of tocilizumab monotherapy after ultra-short-term glucocorticoid treatment in patients with new-onset giant cell arteritis. METHODS: This investigator-initiated, single-arm, single-centre, open-label, proof-of-concept trial with a Simon's two stage design was done at University Hospital Bern, Bern, Switzerland. We enrolled patients aged older than 50 years newly diagnosed with giant cell arteritis (within 4 weeks before the screening visit) satisfying the American College of Rheumatology criteria or with large vessel vasculitis-associated polymyalgia rheumatica. The participants received 500 mg methylprednisolone intravenously for 3 consecutive days. Thereafter, glucocorticoid treatment was discontinued and a single infusion of tocilizumab (8 mg/kg bodyweight) was administered intravenously, followed by weekly subcutaneous tocilizumab injections (162 mg) until week 52. The primary endpoint was the proportion of patients who had remission within 31 days and showed no relapse at week 24. The secondary endpoints were the proportion of patients with complete relapse-free remission of disease at weeks 24 and 52, and time to first remission, first relapse (after induction of remission), and first partial remission. This study is registered with ClinicalTrials.gov, NCT03745586. FINDINGS: From Nov 23, 2018, to Sept 22, 2019, 18 patients were enrolled (12 of 18 were female, 18 of 18 were White) with a median age of 72 (IQR 67-75) years. Overall, 15 of 18 patients had cranial symptoms, ten of 18 had polymyalgia rheumatica symptoms, and 13 of 18 showed a positive histopathology. At the interim analysis, three (25%) of 12 patients were in remission. The null hypothesis could not be rejected, and the study was futile with respect to the primary endpoint. However, 14 (78%) of 18 patients had remission within 24 weeks (mean time to first remission 11·1 weeks, 95% CI 8·3-13·9) and 13 of 18 showed no relapses up to 52 weeks (72%, 47-90). Mean time to first partial remission was 6·2 [3·7-8·7] weeks. Time to first relapse (after induction of remission) could not be estimated as there was no relapse after induction of remission. Overall, three of 18 patients did not respond to treatment and two of 18 discontinued the study due to an adverse event (hepatopathy [one] and diverticulitis [one]). Anterior ischaemic optic neuropathy occurred in one patient. INTERPRETATION: The data show a slow remission-inducing and a lasting remission-maintaining effect of tocilizumab after an ultra-short pulse of glucocorticoids in patients with newly diagnosed giant cell arteritis. As a proof-of-concept study, our data do not allow us to propose clinical recommendations. FUNDING: Bern University Hospital, University of Bern, and F Hoffmann-La Roche.

OMERACT definition and reliability assessment of chronic ultrasound lesions of the axillary artery in giant cell arteritis.

OBJECTIVES: To define chronic ultrasound lesions of the axillary artery (AA) in long-standing giant cell arteritis (GCA) and to evaluate the reliability of the new ultrasound definition in a web-based exercise. METHODS: A structured Delphi, involving an expert panel of the Large Vessel Vasculitis subgroup of the Outcome Measures in Rheumatology (OMERACT) Ultrasound Working Group was carried out. The reliability of the new definition was tested in a 2-round web-based exercise involving 23 experts and using 50 still images each from AA of long-standing and acute GCA patients, as well as 50 images from healthy individuals. RESULTS: The final OMERACT ultrasound definition of chronic changes was based on measurement and appearance of the intima-media complex. The overall reliability of the new definition for chronic ultrasound changes in longstanding GCA of the AA was good to excellent with Light's kappa values of 0.79-0.80 for inter-reader reliability and mean Light's-kappa of 0.88 for intra-reader reliability. The mean inter-rater and intra-rater agreements were 86-87% and 92%, respectively. Good reliabilities were observed comparing the vessels with longstanding versus acute GCA with a mean agreement and kappa values of 81% and 0.63, respectively. CONCLUSION: The new OMERACT ultrasound definition for chronic vasculitis of the AA in GCA revealed a good to excellent inter- and intra-reader reliability in a web-based exercise of experts.