Vascular ultrasound for the diagnosis of giant cell arteritis: a reliability and agreement study based on a standardised training programme

Exploring the limit of image resolution for human expert classification of vascular ultrasound images in giant cell arteritis and healthy subjects: the GCA-US-AI project

OBJECTIVES

Prompt diagnosis of giant cell arteritis (GCA) with ultrasound is crucial for preventing severe ocular and other complications, yet expertise in ultrasound performance is scarce. The development of an artificial intelligence (AI)-based assistant that facilitates ultrasound image classification and helps to diagnose GCA early promises to close the existing gap. In the projection of the planned AI, this study investigates the minimum image resolution required for human experts to reliably classify ultrasound images of arteries commonly affected by GCA for the presence or absence of GCA.

METHODS

Thirty-one international experts in GCA ultrasonography participated in a web-based exercise. They were asked to classify 10 ultrasound images for each of 5 vascular segments as GCA, normal, or not able to classify. The following segments were assessed: (1) superficial common temporal artery, (2) its frontal and (3) parietal branches (all in transverse view), (4) axillary artery in transverse view, and 5) axillary artery in longitudinal view. Identical images were shown at different resolutions, namely 32 × 32, 64 × 64, 128 × 128, 224 × 224, and 512 × 512 pixels, thereby resulting in a total of 250 images to be classified by every study participant.

RESULTS

Classification performance improved with increasing resolution up to a threshold, plateauing at 224 × 224 pixels. At 224 × 224 pixels, the overall classification sensitivity was 0.767 (95% CI, 0.737-0.796), and specificity was 0.862 (95% CI, 0.831-0.888).

CONCLUSIONS

A resolution of 224 × 224 pixels ensures reliable human expert classification and aligns with the input requirements of many common AI-based architectures. Thus, the results of this study substantially guide projected AI development.

An in-depth comparison of vascular inflammation on ultrasound, FDG-PET/CT and MRI in patients with suspected giant cell arteritis

BACKGROUND

Giant cell arteritis (GCA) is a difficult to diagnose large vessel vasculitis. CDUS, FDG-PET/CT and MRI are increasingly used for GCA diagnosis. This study aims to assess vascular wall lesions in GCA suspected patients, directly comparing CDUS, FDG-PET/CT and MRI with each other.

METHODS

In a nested-case control study, consecutive GCA suspected patients were included. Scans were retrospectively assessed by two experts per imaging modality. Inter- and intraobserver agreement using Cohen's or Fleiss Kappa were calculated to assess agreement between experts, a few duplicated scans and between imaging modalities. Sensitivity and specificity of the imaging modalities for overall diagnostic performance and for individual arteries were calculated.

RESULTS

In total, 42 patients were included. Overall diagnostic performance of imaging modalities was comparable. Sensitivity and specificity were highest in the temporal artery for CDUS (76% and 93%; Kappa > 0.7) and MRI (60% and 100%; Kappa > 0.7), and in the vertebral (61% and 100%; Kappa 0.56) and maxillary artery (52% and 100%; Kappa 0.75) for FDG-PET/CT. Agreement between all modalities for a positive temporal artery was 0.76, but only 0.28 between CDUS and FDG-PET/CT. Agreement for the axillary artery was 0.7 between CDUS and FDG-PET/CT.

CONCLUSION

The temporal artery can be assessed by CDUS and MRI with good sensitivity and high specificity, and the axillary artery by CDUS and FDG-PET/CT with high agreement between the two modalities. In addition, the vertebral and maxillary artery can be assessed by FDG-PET/CT with good sensitivity and specificity, however the vertebral artery had moderate interobserver agreement.

OMERACT GCA phantom project: validation of a 3D-printed ultrasound training phantom for diagnosis of giant cell arteritis

OBJECTIVE

Ultrasonography is crucial for diagnosing giant cell arteritis (GCA); however, training opportunities are rare. This study tested the reliability of ultrasonography findings and measurements of the intima-media thickness (IMT) among ultrasonography experts by using phantoms of the axillary (AA) and temporal arteries (TA) created with high-resolution 3D printing.

METHODS

Twenty-eight participants from 12 European countries received eight sets of phantoms of the AA and the superficial TA (including common, frontal and parietal branches), which were examined in a blinded fashion according to a predefined protocol and evaluated based on Outcome Measures in Rheumatology (OMERACT) GCA ultrasound definitions. Due to difficulties with the delineation of the intima-media complex, the parietal branch of the phantoms was modified, and a second round was conducted. The IMT was measured, and phantoms were classified as normal or vasculitic.

RESULTS

In both rounds, the phantoms were correctly classified as normal/abnormal in >81% of cases yielding a Fleiss' kappa of 0.80 (95% CI 0.78 to 0.81) in round 1 and 0.74 (95% CI 0.72 to 0.75) in round 2. IMT measurements revealed an intraclass correlation coefficient (ICC 1.1) of 0.98 (95% CI 0.98 to 0.99) in both rounds. Intrarater reliability was good with a median Cohens Kappa of 0.83 and median ICC of 0.78.

CONCLUSION

The study demonstrated high reliability among ultrasound experts in applying the OMERACT ultrasound definitions for GCA and in measuring the IMT using a 3D-printed phantom of the AA and TA. This phantom could assist clinicians in training to assess the large arteries of patients with suspected or established GCA.

Reliability of the OMERACT Giant cell arteritis Ultrasonography Score (OGUS): results of a patient-based exercise involving experts and non-experts in vascular ultrasonography

OBJECTIVE

To test the reliability of the Outcome Measures in Rheumatology Giant cell arteritis (GCA) Ultrasonography Score (OGUS) and other composite scores in a patient-based exercise involving experts and non-experts in vascular ultrasonography.

METHODS

Six GCA patients were scanned twice (two rounds separated ≥3 hours) by 12 experts and 12 non-experts. Non-experts received 90 min of theoretical and 240 min of practical training between rounds 1 and 2. Ultrasonography was conducted on temporal arteries (common superficial, frontal and parietal branches) and axillary arteries bilaterally to calculate the OGUS, the Southend score and the Halo count. Inter-reader and intra-reader reliability were assessed by intraclass correlation coefficient (ICC).

RESULTS

Mean age of GCA patients was 78±5.1 years, 2 (33.3%) were women, and all were in clinical remission. Expert inter-reader ICC of the OGUS was 0.60 in both rounds, 0.40 in round 1 and 0.51 in round 2 for the Southend score and 0.45 and 0.52, respectively, for the Halo count. Median ICCs for intra-reader reliability were 0.86, 0.73 and 0.65 for the OGUS, Southend score and Halo count, respectively.For non-experts, inter-reader ICCs in round 1 were 0.20 for the OGUS, 0.20 for a normalised Southend score (=score divided by available segments) and 0.35 for a normalised Halo count. After training, inter-reader reliability ICCs improved to 0.52, 0.29 and 0.54, respectively.

CONCLUSION

Inter-reader reliability was fair to moderate, and intra-reader reliability was good for OGUS, Southend score and Halo count among experts. Inter-reader reliability of non-experts in vascular ultrasonography improved after the training.

Cranial involvement in giant cell arteritis

Since its first clinical description in 1890, extensive research has advanced our understanding of giant cell arteritis, leading to improvements in both diagnosis and management for affected patients. Imaging studies have shown that the disease frequently extends beyond the typical cranial arteries, also affecting large vessels such as the aorta and its proximal branches. Meanwhile, advances in comprehending the underlying pathophysiology of giant cell arteritis have given rise to numerous potential therapeutic agents, which aim to minimise the need for glucocorticoid treatment and prevent flares. Classification criteria for giant cell arteritis, as well as recommendations for management, imaging, and treat-to-target have been developed or updated in the last 5 years, and current research encompasses a broad spectrum covering basic, translational, and clinical research. In this Series paper, we aim to discuss the current understanding of giant cell arteritis with cranial manifestations, describe the clinical approach to this condition, and explore future directions in research and patient care.

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.

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.

Quality standards for the care of people with giant cell arteritis in secondary care

OBJECTIVE

GCA is the commonest primary systemic vasculitis in adults, with significant health economic costs and societal burden. There is wide variation in access to secondary care GCA services, with 34% of hospitals in England not having any formal clinical pathway. Quality standards provide levers for change to improve services.

METHODS

The multidisciplinary steering committee were asked to anonymously put forward up to five aspects of service essential for best practice. Responses were qualitatively analysed to identify common themes, subsequently condensed into domain headings, and ranked in order of importance. Quality standards and metrics for each domain were drafted, requiring a minimum 75% agreement.

RESULTS

13 themes were identified from the initial suggestions. Nine quality standards with auditable metrics were developed from the top 10 themes. Patient Access, glucocorticoid use, pathways, ultrasonography, temporal artery biopsy, PET scan access, rheumatology/ophthalmology expertise, education, multidisciplinary working have all been covered in these quality standards. Access to care is a strand that has run through each of the developed standards. An audit tool was developed as part of this exercise.

CONCLUSION

These are the first consensus auditable quality standards developed by clinicians from rheumatology and ophthalmology, nursing representatives and involvement of a patient charity. We hope that these standards will be adopted by commissioning bodies to provide levers for change from the improvement of patient care of individuals with GCA.

Giant cell arteritis: reviewing the advancing diagnostics and management

Giant Cell Arteritis (GCA) is well known to be a critical ischaemic disease that requires immediate medical recognition to initiate treatment and where one in five people still suffer visual loss. The immunopathophysiology has continued to be characterised, and the influencing of ageing in the development of GCA is beginning to be understood. Recent national and international guidelines have supported the directed use of cranial ultrasound to reduce diagnostic delay and improve clinical outcomes. Immediate high dose glucocorticoids remain the standard emergency treatment for GCA, with a number of targeted agents that have been shown in clinical trials to have superior clinical efficacy and steroid sparing effects. The aim of this review was to present the latest advances in GCA that have the potential to influence routine clinical practice.

Extended ultrasound examination identifies more large vessel involvement in patients with giant cell arteritis

OBJECTIVES

To compare limited with a more extended ultrasound examination (anteromedial ultrasound, A2-ultrasound) to detect large vessel (LV) involvement in patients with newly diagnosed GCA.

METHODS

Patients with new-onset GCA were included at the time of diagnosis. All patients were examined using limited ultrasound (ultrasound of the axillary artery as visualized in the axilla) and an extended A2-ultrasound method (which also includes the carotid, vertebral, subclavian and proximal axillary arteries), in addition to temporal artery ultrasound.

RESULTS

One hundred and thirty-three patients were included in the study. All patients fulfilled the criteria according to a proposed extension of the 1990 ACR classification criteria for GCA and had a positive ultrasound examination at diagnosis. Ninety-three of the 133 GCA patients (69.9%) had LV involvement when examined by extended A2-ultrasound, compared with only 56 patients (42.1%) by limited ultrasound (P < 0.001). Twelve patients (9.0%) had vasculitis of the vertebral arteries as the only LVs involved. Five patients (3.8%) would have been missed as having GCA if only limited ultrasound was performed. Forty patients (30.0%) had isolated cranial GCA, 21 patients (15.8%) had isolated large vessel GCA and 72 patients (54.1%) had mixed-GCA.

CONCLUSION

Extended A2-ultrasound examination identified more patients with LV involvement than the limited ultrasound method. However, extended A2-ultrasound requires high expertise and high-end equipment and should be performed by ultrasonographers with adequate training.

Norwegian society of rheumatology recommendations on diagnosis and treatment of patients with giant cell arteritis

Objective

To provide clinical guidance to Norwegian Rheumatologists and other clinicians involved in diagnosing and treating patients with giant cell arteritis (GCA).

Methods

The available evidence in the field was reviewed, and the GCA working group wrote draft guidelines. These guidelines were discussed and revised according to standard procedures within the Norwegian Society of Rheumatology. The European Alliance of Associations for Rheumatology (EULAR) recommendations for imaging and treatment in large vessel vasculitis and the British Society for Rheumatology (BSR) guidelines for diagnostics and treatment in GCA informed the development of the current guidelines.

Results

A total of 13 recommendations were developed. Ultrasound is recommended as the primary diagnostic test. In patients with suspected GCA, treatment with high doses of Prednisolone (40-60 mg) should be initiated immediately. For patients with refractory disease or relapse, Methotrexate (MTX) should be used as the first-line adjunctive therapy, followed by tocilizumab (TCZ).

Conclusion

Norwegian recommendations for diagnostics and treatment to improve management and outcome in patients with GCA were developed.

Predictive Factors of Giant Cell Arteritis in Polymyalgia Rheumatica Patients

Polymyalgia rheumatica (PMR) is an inflammatory rheumatism of the shoulder and pelvic girdles. In 16 to 21% of cases, PMR is associated with giant cell arteritis (GCA) that can lead to severe vascular complications. Ruling out GCA in patients with PMR is currently a critical challenge for clinicians. Two GCA phenotypes can be distinguished: cranial GCA (C-GCA) and large vessel GCA (LV-GCA). C-GCA is usually suspected when cranial manifestations (temporal headaches, jaw claudication, scalp tenderness, or visual disturbances) occur. Isolated LV-GCA is more difficult to diagnose, due to the lack of specificity of clinical features which can be limited to constitutional symptoms and/or unexplained fever. Furthermore, many studies have demonstrated the existence-in varying proportions-of subclinical GCA in patients with apparently isolated PMR features. In PMR patients, the occurrence of clinical features of C-GCA (new onset temporal headaches, jaw claudication, or abnormality of temporal arteries) are highly predictive of C-GCA. Additionally, glucocorticoids' resistance occurring during follow-up of PMR patients, the occurrence of constitutional symptoms, or acute phase reactants elevation are suggestive of associated GCA. Research into the predictive biomarkers of GCA in PMR patients is critical for selecting PMR patients for whom imaging and/or temporal artery biopsy is necessary. To date, Angiopoietin-2 and MMP-3 are powerful for predicting GCA in PMR patients, but these results need to be confirmed in further cohorts. In this review, we discuss the diagnostic challenges of subclinical GCA in PMR patients and will review the predictive factors of GCA in PMR patients.

Current developments in the diagnosis and treatment of giant cell arteritis

Giant cell arteritis is the most common vasculitis in adults above 50 years old. The disease is characterized by granulomatous inflammation of medium and large arteries, particularly the temporal artery, and is associated acutely with headache, claudication, and visual disturbances. Diagnosis of the disease is often complicated by its protean presentation and lack of consistently reliable testing. The utility of color doppler ultrasound at the point-of-care and FDG-PET in longitudinal evaluation remain under continued investigation. Novel techniques for risk assessment with Halo scoring and stratification through axillary vessel ultrasound are becoming commonplace. Moreover, the recent introduction of the biologic tocilizumab marks a paradigm shift toward using glucocorticoid-sparing strategies as the primary treatment modality. Notwithstanding these developments, patients continue to have substantial rates of relapse and biologic agents have their own side effect profile. Trials are underway to answer questions about optimal diagnostic modality, regiment choice, and duration.

Evolution of ultrasound in giant cell arteritis

Ultrasound (US) is being increasingly used to diagnose Giant Cell Arteritis (GCA). The traditional diagnostic Gold Standard has been temporal artery biopsy (TAB), but this is expensive, invasive, has a false-negative rate as high as 60% and has little impact on clinical decision-making. A non-compressible halo with a thickened intima-media complex (IMC) is the sonographic hallmark of GCA. The superficial temporal arteries (STA) and axillary arteries (AA) are the most consistently inflamed arteries sonographically and imaging protocols for evaluating suspected GCA should include at least these two arterial territories. Studies evaluating temporal artery ultrasound (TAUS) have varied considerably in size and methodology with results showing wide discrepancies in sensitivity (9–100%), specificity (66–100%), positive predictive value (36–100%) and negative predictive value (33–100%). Bilateral halos increase sensitivity as does the incorporation of pre-test probability, while prior corticosteroid use decreases sensitivity. Quantifying sonographic vasculitis using Halo Counts and Halo Scores can predict disease extent/severity, risk of specific complications and likelihood of treatment response. Regression of the Halo sign has been observed from as little as 2 days to as late as 7 months after initiation of immunosuppressive treatment and occurs at different rates in STAs than AAs. US is more sensitive than TAB and has comparable sensitivity to MRI and PET/CT. It is time-efficient, cost-effective and allows for the implementation of fast-track GCA clinics which substantially mitigate the risk of irreversible blindness. Algorithms incorporating combinations of imaging modalities can achieve a 100% sensitivity and specificity for a diagnosis of GCA. US should be a standard first line investigation in routine clinical care of patients with suspected GCA with TAB reserved only for those having had a normal US in the context of a high pre-test probability.

Fever Correlation with Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) Concentrations in Patients with Isolated Polymyalgia Rheumatica (PMR): A Retrospective Comparison Study between Hospital and Out-of-Hospital Local Registries

Background: Polymyalgia rheumatica (PMR) is the most common systemic inflammatory rheumatic disease affecting the elderly. Giant cell arteritis (GCA) is a granulomatous vasculitis affecting the aorta and its branches associated with PMR in up to 20% of cases. In recent studies based on university hospital registries, fever correlated with the erythrocyte sedimentation rate (ESR) but not with C-reactive protein (CRP) concentrations at the time of diagnosis in patients with isolated PMR. A long delay to a PMR diagnosis was suggested to explain this discrepancy, possibly caused by laboratory alterations (for instance, anemia of chronic disease type) that can influence only ESR. We performed a retrospective comparison study between the university hospital and two out-of-hospital public ambulatory databases, searching for any differences in fever/low-grade fever correlation with ESR and CRP. Methods: We identified all patients with newly diagnosed PMR between 2013 and 2020, only including patients who had a body temperature (BT) measurement at the time of diagnosis and a follow-up of at least two years. We considered BT as normal at <37.2 °C. Routine diagnostic tests for differential diagnostics were performed at the time of diagnosis and during follow-ups, indicating the need for more in-depth investigations if required. The GCA was excluded based on the presence of suggestive signs or symptoms and routine ultrasound examination of temporal, axillary, subclavian, and carotid arteries by experienced ultrasonographers. Patients with malignancies, chronic renal disease, bacterial infections, and body mass index (BMI) > 30 kg/m2 were excluded, as these conditions can increase CRP and/or ESR. Finally, we used the Cumulative Illness Rating Scale (CIRS) for quantifying the burden of comorbidities and excluded patients with a CIRS index > 4 as an additional interfering factor. Results: We evaluated data from 169 (73 from hospital and 96 from territorial registries) patients with newly diagnosed isolated PMR. Among these, 77.7% were female, and 61.5% of patients had normal BT at the time of diagnosis. We divided the 169 patients into two cohorts (hospital and territorial) according to the first diagnostic referral. Age at diagnosis, ESR, CRP, median hemoglobin (HB), and diagnostic delay (days from first manifestations to final diagnosis) were statistically significantly different between the two cohorts. However, when we assessed these data according to BT in the territorial cohort, we found a statistical difference only between ESR and BT (46.39 ± 19.31 vs. 57.50 ± 28.16; p = 0.026). Conclusions: ESR but not CRP correlates with fever/low-grade fever at the time of diagnosis in PMR patients with a short diagnosis delay regardless of HB levels. ESR was the only variable having a statistically significant correlation with BT in a multilevel regression analysis adjusted for cohorts (β = 0.312; p = 0.014).

Looking ahead: giant-cell arteritis in 10 years time

Although great improvements have been achieved in the fields of diagnosing and treating patients with giant-cell arteritis (GCA) in the last decades, several questions remain unanswered. The progressive increase in the number of older people, together with growing awareness of the disease and use of advanced diagnostic tools by healthcare professionals, foretells a possible increase in both prevalence and number of newly diagnosed patients with GCA in the coming years. A thorough clarification of pathogenetic mechanisms and a better definition of clinical subsets are the first steps toward a better understanding of the disease and, subsequently, toward a better use of existing and future therapeutic options. Examination of the role of different imaging techniques for GCA diagnosing and monitoring, optimization, and personalization of glucocorticoids and other immunosuppressive agents, further development and introduction of novel drugs, identification of prognostic factors for long-term outcomes and management of treatment discontinuation will be the central topics of the research agenda in years to come.

The diagnostic accuracy of temporal artery ultrasound and temporal artery biopsy in giant cell arteritis: A single center Australian experience over 10 years

Aim

Method

Results

Conclusion

Diagnostic accuracy of vascular ultrasound in patients with suspected giant cell arteritis (EUREKA): a prospective, multicentre, non-interventional, cohort study

BACKGROUND

Temporal artery biopsy is considered the diagnostic gold standard for giant cell arteritis, despite approximately 39% of patients who are negative for the condition by biopsy subsequently being given a clinical diagnosis of giant cell arteritis. We aimed to assess the diagnostic accuracy of ultrasound examination in patients with suspected giant cell arteritis.

METHODS

In this prospective, multicentre, non-interventional, cohort study (evaluation of ultrasound's role in patients suspected of having extracranial and cranial giant cell arteritis; EUREKA), we consecutively recruited patients aged 50 years or older, with clinically suspected giant cell arteritis from three Danish hospitals (South West Jutland Hospital in Esbjerg, Silkeborg Regional Hospital, and Rigshospitalet, Glostrup). Participants had a bilateral ultrasound of the temporal, facial, common carotid, and axillary arteries. Ultrasounds were done by ultrasonographers who were systematically trained in vascular ultrasound using appropriate equipment and settings. Participants then had a temporal artery biopsy within 7 days of initiation of corticosteroid treatment. A blinded ultrasound expert assessed all ultrasound images. Ultrasound vasculitis was defined in cranial arteries as a homogeneous, hypoechoic, intimamedia complex thickness and a positive compression sign and as a homogeneous intimamedia complex of 1 mm in thickness or wider in the axillary arteries and of 1·5 mm thickness or wider in the common carotid artery. Participants were followed up at 6 months. During this 6 month period, clinicians were able to collect data from all clinical examinations to enable a full clinical diagnosis at 6 months. Clinical diagnosis was based on the expert opinion of the treating rheumatologist. The diagnostic criterion standard was diagnosis confirmed after 6 months of follow-up. We used logistic regression analyses to calculate the odds ratio and 95% CI of ultrasound as a predictor for giant cell arteritis.

FINDINGS

Between April 1, 2014, and July 31, 2017, 118 patients were screened for inclusion, of whom 106 had both ultrasound examinations and an eligible temporal artery biopsy and were included in the intention-to-diagnose population. The mean age was 72·7 years (SD 7·9), 63 (59%) participants were women, and 43 (41%) were men. Temporal artery biopsy was positive in 46 (43%) of 106 patients, and 62 (58%) of 106 patients had a clinically confirmed diagnosis of giant cell arteritis at 6 months (temporal artery biopsy sensitivity 74% [95% CI 62-84], specificity 100% [95% CI 92-100]). Cranial artery ultrasound was positive in all patients who had a positive temporal artery biopsy, and seven (58%) of 12 patients who were positive by ultrasound and negative by temporal artery biopsy were confirmed to have large-vessel giant cell arteritis via other imaging methods. The sensitivity of ultrasound diagnosis of giant cell arteritis was 94% (84-98) and specificity was 84% (70-93). Logistic regression analysis confirmed that ultrasound was the strongest baseline predictor for a clinically confirmed diagnosis of giant cell arteritis at 6 months (crude odds ratio 76·6 [95% CI 21·0-280·0]; adjusted for sex and age 141·0 [27·0-743·0]).

INTERPRETATION

Vascular ultrasound might effectively replace temporal artery biopsy as a first-line diagnostic method in patients suspected of having giant cell arteritis when done by systematically trained ultrasonographers using appropriate equipment and settings.

FUNDING

The Institute for Regional Research at Hospital of Southwest Jutland, Esbjerg, Denmark.

Diagnosing Giant Cell Arteritis: A Comprehensive Practical Guide for the Practicing Rheumatologist

Giant cell arteritis (GCA) is the most common large vessel vasculitis in the elderly population. In recent years, advanced imaging has changed the way GCA can be diagnosed in many locations. The GCA fast-track clinic (FTC) approach combined with ultrasound (US) examination allows prompt treatment and diagnosis with high certainty. FTCs have been shown to improve prognosis while being cost effective. However, all diagnostic modalities are highly operator dependent, and in many locations expertise in advanced imaging may not be available. In this paper, we review the current evidence on GCA diagnostics and propose a simple algorithm for diagnosing GCA for use by rheumatologists not working in specialist centres.

Ultrasonography in the diagnosis and follow-up of giant cell arteritis

Colour Doppler ultrasonography is the first measure to allow objective bedside assessment of GCA. This article discusses the evidence using the OMERACT filter. Consensus definitions for ultrasonographic changes were agreed upon by a Delphi process, with the 'halo' and 'compression' signs being characteristic. The halo is sensitive to change, disappearing within 2-4 weeks of starting glucocorticoids. Ultrasonography has moderate convergent validity with temporal artery biopsy in a pooled analysis of 12 studies including 965 participants [κ = 0.44 (95% CI 0.38, 0.50)]. The interobserver and intra-observer reliabilities are good (κ = 0.6 and κ = 0.76-0.78, respectively) in live exercises and excellent when assessing acquired images and videos (κ = 0.83-0.87 and κ = 0.88, respectively). Discriminant validity has been tested against stroke and diabetes mellitus (κ=-0.16 for diabetes). Machine familiarity and adequate examination time improves performance. Ultrasonography in follow-up is not yet adequately defined. Some patients have persistent changes in the larger arteries but these do not necessarily imply treatment failure or predict relapses.