Clinical Manifestations and Prognosis of Giant Cell Arteritis: A Retrospective Cohort Study.

The aim of the study was to evaluate the clinical manifestations and survival of patients with giant cell arteritis (GCA). MATERIALS AND METHODS: . A retrospective study included 166 patients with newly diagnosed GCA. Clinical, laboratory, and instrumental data and three sets of classification criteria were used to confirm the diagnosis: the American College of Rheumatology (ACR) 1990, the revised ACR criteria of 2016 and/or the new ACR and European Alliance of Rheumatologic Associations (EULAR) 2022 criteria. Some of the patients underwent instrumental investigations: temporal artery ultrasound Doppler (n = 61), contrast-enhanced computed tomography (n = 5), CT angiography (n = 6), magnetic resonance imaging (n = 4), MR angiography (n = 3), and 18F-FDG PET/CT (n = 47). Overall and recurrence-free survival rates were analyzed using survival tables and Kaplan-Meier method. RESULTS: . The most frequent first manifestations of GCA were headache (81.8%), weakness (64%), fever (63.8%), and symptoms of rheumatic polymyalgia (56.6%). Changes in temporal arteries in color duplex scanning were detected in 44 out of 61 patients. GCs therapy was performed in all patients who agreed to be treated (n = 158), methotrexate was used in 49 out of 158 patients, leflunomide in 9 patients. In 45 (28.5%) out of 158 patients, a stable remission was achieved as a result of GC monotherapy; in 120 (75.9%) patients, long-term maintenance therapy with GCs was required to prevent exacerbations, including 71 (44.9%) patients in combination with methotrexate or other immunosuppressive drugs. The follow-up period of patients with a history of relapses was 21.0 (8.0-54.0) months. Relapses developed in 73 (46.2%) patients. The overall one-year survival rate was 97.1% [95% CI 94.3; 99.9], and the five-year survival rate of patients was 94.6% [95% CI 90.2; 99.0]. The one-year relapse-free survival rate was 86.4% [95% CI 80.5; 92.3], and the five-year relapse-free survival rate was 52.4% [95% CI 42.0; 62.8]. Twelve (7.2%) of 166 patients died. The cause of death was myocardial infarction in two patients, stroke in two patients, and breast cancer in one patient; in the remaining seven cases, the cause of death was not determined. CONCLUSIONS: : Given the high frequency of disease exacerbation, patients with GCA require long-term follow-up, especially during the first year after diagnosis.

Diagnostic Strategy Using Color Doppler Ultrasound of Temporal Arteries in Patients With High Clinical Suspicion of Giant Cell Arteritis : A Prospective Cohort Study.

BACKGROUND: Giant cell arteritis (GCA) is the most prevalent systemic vasculitis in people older than 50 years. Any delay in diagnosis impairs patients' quality of life and can lead to permanent damage, particularly vision loss. OBJECTIVE: To evaluate a diagnostic strategy for GCA using color Doppler ultrasound of the temporal artery as a first-line diagnostic test, temporal artery biopsy (TAB) as a secondary test, and physician expertise as the reference method. DESIGN: Prospective multicenter study with a 2-year follow-up. (ClinicalTrials.gov: NCT02703922). SETTING: Patients were referred by their general practitioner or ophthalmologist to a physician with extensive experience in GCA diagnosis and management in one of the participating centers: 4 general and 2 university hospitals. PATIENTS: 165 patients with high clinical suspicion of GCA, aged 79 years (IQR, 73 to 85 years). INTERVENTION: The diagnostic procedure was ultrasound, performed less than 7 days after initiation of corticosteroid therapy. Only ultrasound-negative patients underwent TAB. MEASUREMENTS: Bilateral temporal halo signs seen on ultrasound were considered positive. Ultrasound and TAB results were compared with physician-diagnosed GCA based on clinical findings and other imaging. RESULTS: Diagnosis of GCA was confirmed in 44%, 17%, and 21% of patients by ultrasound, TAB, and clinical expertise and/or other imaging tests, respectively. Their diagnosis remained unchanged at 1 month, and 2 years for those with available follow-up data. An alternative diagnosis was made in 18% of patients. The proportion of ultrasound-positive patients among patients with a clinical GCA diagnosis was 54% (95% CI, 45% to 62%). LIMITATION: Small sample size, no blinding of ultrasound and TAB results, lack of an objective gold-standard comparator, and single diagnostic strategy. CONCLUSION: By using ultrasound of the temporal arteries as a first-line diagnostic tool in patients with high clinical suspicion of GCA, further diagnostic tests for patients with positive ultrasound were avoided. PRIMARY FUNDING SOURCE: Tender "Recherche CH-CHU Poitou-Charentes 2014."

Broadening the clinical spectrum of giant cell arteritis: from the classic cranial to the predominantly extracranial pattern of the disease.

INTRODUCTION: Giant cell arteritis (GCA) is a large vessel (LV) vasculitis that affects people aged 50 years and older. Classically, GCA was considered a disease that involved branches of the carotid artery. However, the advent of new imaging techniques has allowed us to reconsider the clinical spectrum of this vasculitis. AREASCOVERED: This review describes clinical differences between patients with the cranial GCA and those with a predominantly extracranial LV-GCA disease pattern. It highlights differences in the frequency of positive temporal artery biopsy depending on the predominant disease pattern and emphasizes the relevance of imaging techniques to identify patients with LV-GCA without cranial ischemic manifestations. The review shows that so far there are no well-established differences in genetic predisposition to GCA regardless of the predominant phenotype. EXPERT COMMENTARY: The large branches of the extracranial arteries are frequently affected in GCA. Imaging techniques are useful to identify the presence of 'silent' GCA in people presenting with polymyalgia rheumatica or with nonspecific manifestations. Whether these two different clinical presentations of GCA constitute a continuum in the clinical spectrum of the disease or whether they may be related but are definitely different conditions needs to be further investigated.

Giant Cell Arteritis. / Riesenzellarteriitis.

Giant cell arteritis (GCA) is the most common primary vasculitis and is associated with potential bilateral blindness. Neither clinical nor laboratory evidence is simple and unequivocal for this disease, which usually requires rapid and reliable diagnosis and therapy. The ophthalmologist should consider GCA with the following ocular symptoms: visual loss or visual field defects, transient visual disturbances (amaurosis fugax), diplopia, eye pain, or new onset head or jaw claudication. An immediate ophthalmological examination with slit lamp, ophthalmoscopy, and visual field, as well as color duplex ultrasound of the temporal artery should be performed. If there is sufficient clinical suspicion of GCA, corticosteroid therapy should be initiated immediately, with prompt referral to a rheumatologist/internist and, if necessary, temporal artery biopsy should be arranged. Numerous developments in modern imaging with colour duplex ultrasonography, MRI, and PET-CT have the potential to compete with the classical, well-established biopsy of a temporal artery. Early determination of ESR and CRP may support RZA diagnosis. Therapeutically, steroid-sparing immunosuppression with IL-6 blockade or methotrexate can be considered. These developments have led to a revision of both the classification criteria and the diagnostic and therapeutic recommendations of the American College of Rheumatologists and the European League against Rheumatism, which are summarised here for ophthalmology.

Performance of a fast-track pathway for giant cell arteritis in Waikato, Aotearoa New Zealand.

AIMS: Giant cell arteritis (GCA) is the most common primary vasculitis in adults over 50 years of age. To facilitate early diagnosis and reduce harms from corticosteroids and temporal artery biopsies, fast-track pathways have been established. We review the benefits of the fast-track pathway set up in Waikato, Aotearoa New Zealand. METHODS: Patients were collected prospectively as part of the fast-track pathway from 2014 to 2022. Their records were then reviewed retrospectively to collect data on clinical features, investigations and treatment. RESULTS: There were 648 individual patients over the study period who had a colour Doppler ultrasound (CDUS) of the temporal arteries. There were 17 true positive CDUS, giving a sensitivity of 10.3% (95% confidence interval [CI] 6.3-15.5%) and specificity of 99.8% (95% CI 99.1-100%). Patients with GCA and a positive scan had significantly fewer steroids than those with GCA and a negative scan (p=0.0037). There were 376 patients discharged after a CDUS who did not have a diagnosis of GCA, resulting in reduced corticosteroid and temporal artery biopsy exposure. CONCLUSIONS: This is a real-life study that reflects the benefits of fast-track pathways in Aotearoa New Zealand to patients and healthcare systems. It also shows the effect of corticosteroids on positive CDUS, an important consideration when setting up an fast-track pathway.

Development of a diagnostic prediction model for giant cell arteritis by sequential application of Southend Giant Cell Arteritis Probability Score and ultrasonography: a prospective multicentre study.

BACKGROUND: Giant cell arteritis is a critically ischaemic disease with protean manifestations that require urgent diagnosis and treatment. European Alliance of Associations for Rheumatology (EULAR) recommendations advocate ultrasonography as the first investigation for suspected giant cell arteritis. We developed a prediction tool that sequentially combines clinical assessment, as determined by the Southend Giant Cell Arteritis Probability Score (SGCAPS), with results of quantitative ultrasonography. METHODS: This prospective, multicentre, inception cohort study included consecutive patients with suspected new onset giant cell arteritis referred to fast-track clinics (seven centres in Italy, the Netherlands, Spain, and UK). Final clinical diagnosis was established at 6 months. SGCAPS and quantitative ultrasonography of temporal and axillary arteries with three scores (ie, halo count, halo score, and OMERACT GCA Score [OGUS]) were performed at diagnosis. We developed prediction models for diagnosis of giant cell arteritis by multivariable logistic regression analysis with SGCAPS and each of the three ultrasonographic scores as predicting variables. We obtained intraclass correlation coefficient for inter-rater and intra-rater reliability in a separate patient-based reliability exercise with five patients and five observers. FINDINGS: Between Oct 1, 2019, and June 30, 2022, we recruited and followed up 229 patients (150 [66%] women and 79 [34%] men; mean age 71 years [SD 10]), of whom 84 were diagnosed with giant cell arteritis and 145 with giant cell arteritis mimics (controls) at 6 months. SGCAPS and all three ultrasonographic scores discriminated well between patients with and without giant cell arteritis. A reliability exercise showed that the inter-rater and intra-rater reliability was high for all three ultrasonographic scores. The prediction model combining SGCAPS with the halo count, which was termed HAS-GCA score, was the most accurate model, with an optimism-adjusted C statistic of 0·969 (95% CI 0·952 to 0·990). The HAS-GCA score could classify 169 (74%) of 229 patients into either the low or high probability groups, with misclassification observed in two (2%) of 105 patients in the low probability group and two (3%) of 64 of patients in the high probability group. A nomogram for easy application of the score in daily practice was created. INTERPRETATION: A prediction tool for giant cell arteritis (the HAS-GCA score), combining SGCAPS and the halo count, reliably confirms and excludes giant cell arteritis from giant cell arteritis mimics in fast-track clinics. These findings require confirmation in an independent, multicentre study. FUNDING: Royal College of Physicians of Ireland, FOREUM.

Epidemiology of giant cell arteritis in Waikato, Aotearoa New Zealand.

AIM: Giant cell arteritis (GCA) is the most common primary vasculitis in adults over 50 years of age. Our primary objective was to assess the incidence and prevalence of GCA in Waikato in a bid to deepen our understanding of the epidemiology of GCA in Aotearoa New Zealand. METHODS: From January 2014 to December 2022, cases of GCA were identified prospectively and retrospectively through temporal artery ultrasound request lists and temporal artery biopsy histology reports. Using electronic health records, data were collected retrospectively on patient demographics and clinical features. These were used to calculate the incidence, prevalence and standardised mortality ratio (SMR) of GCA in Waikato. RESULTS: There were 214 patients diagnosed with GCA over the 9-year period. The majority of patients were European (93.9%, 201/214) with Maori patients being significantly younger than European patients. The mean annual incidence of clinical GCA was 14.7 per 100,000 people over 50 years (95% confidence interval [CI] 12.7-16.6). The SMR was 1.18 (95% CI 0.83-1.52). CONCLUSION: This is the largest study to date on the epidemiology of GCA in Aotearoa New Zealand. The incidence of GCA is comparable to other studies performed in Aotearoa New Zealand and appears to be stable over time. GCA is uncommon in Maori, Pacific Islander and Asian ethnic groups.

Giant cell arteritis: insights from a monocentric retrospective cohort study.

Giant cell arteritis (GCA), more common in Northern European populations, has limited data in Arabcountries. Our study reports GCA's clinical manifestations in Jordan and reviews published research on GCA across Arab nations. In this retrospective analysis, GCA patients diagnosed from January 2007 to March 2019 at a Jordanian academic medical center were included through referrals for temporal artery biopsy (TAB). A comprehensive search in PubMed, Scopus, and the DOAJ (Directory of Open Access Journals) databases was conducted to identify all relevant English-language manuscripts from Arab countries on GCA without time limitations. Among 59 diagnosed GCA patients, 41 (69.5%) were clinically diagnosed with a negative TAB, and 19 (30.5%) had a positive result. Females comprised 74.6% (n = 44) with 1:3 male-female ratio. The mean age at diagnosis was 67.3 (± 9.5) years, with most presenting within two weeks (n = 40, 67.8%). Headache was reported by 54 patients (91.5%). Elevated ESR occurred in 51 patients (78%), with a mean of 81 ± 32.2 mm/hr. All received glucocorticoids for 13.1 ± 10 months. Azathioprine, Methotrexate, and Tocilizumab usage was 15.3% (n = 9), 8.5% (n = 5), and 3.4% (n = 2), respectively. Remission was observed in 57.6% (n=34), and 40.7% (n = 24) had a chronic clinical course on treatment. Males had higher biopsy-based diagnoses (p = .008), and biopsy-diagnosed patients were older (p = .043). The literature search yielded only 20 manuscripts originating in the Arab world. The predominant study types included case reports and retrospective analyses, with only one case series and onecase-control study.

Should all patients with polymyalgia rheumatica have a vascular ultrasound assessment?

There is a growing appreciation that both giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are closely interrelated conditions that have significant overlap in aetiology, clinical characteristics and treatment regimens. Subclinical GCA in PMR is becoming increasingly recognised, and there is evolving evidence that this may be a more aggressive disease phenotype than PMR. Ultrasound (US) lends itself well as a screening tool for GCA in PMR; it is inexpensive, non-invasive, widely available, lacks ionising radiation, may be performed at the bedside and is recommended by EULAR as a first-line investigation for suspected GCA. There is insufficient evidence to currently recommend that all patients with PMR should have a US assessment for vascular involvement. However, as clinical and laboratory parameters alone do not accurately diagnose patients with subclinical GCA, we suggest that vascular US will be increasingly performed by rheumatologists in practice to identify these patients with PMR, preferably as part of larger prospective outcome studies.

Analysis of Temporal Artery Biopsy by Provider Across a Large Multi-State Health Care Network.

Temporal artery biopsy (TAB) is the standard test for diagnosing giant cell arteritis. Our objective was to determine which specialists perform TABs and if there is variation across the United States. We performed a cross-sectional analysis in a multi-state health care system, evaluating differences between observed counts of surgical specialty by region, positive diagnoses by region, and positive diagnoses by specialty. Temporal arterial biopsy was performed on 3825 patients with the proportion of specialties performing TAB differing between regions. Temporal artery biopsy was performed by a significantly higher percentage of general surgeons in the Midwest (53.6%) and less vascular surgeons in the West (30.4%). The percentage of positive diagnoses was higher for vascular surgeons (32.7%). We concluded that TAB is performed by physicians of many specialties with the specialty performing most of these procedures varying by region. There is also a difference in the rate of positive diagnoses that varies with surgical specialty.

Halo sign on temporal artery ultrasound versus temporal artery biopsy for giant cell arteritis.

BACKGROUND: Giant cell arteritis (GCA) is a systemic, inflammatory vasculitis primarily affecting people over the age of 50 years. GCA is treated as a medical emergency due to the potential for sudden, irreversible visual loss. Temporal artery biopsy (TAB) is one of the five criteria of the American College of Rheumatology (ACR) 1990 classification, which is used to aid the diagnosis of GCA. TAB is an invasive test, and it can be slow to obtain a result due to delays in performing the procedure and the time taken for histopathologic assessment. Temporal artery ultrasonography (US) has been demonstrated to show findings in people with GCA such as the halo sign (a hypoechoic circumferential wall thickening due to oedema), stenosis or occlusion that can help to confirm a diagnosis more swiftly and less invasively, but requiring more subjective interpretation. This review will help to determine the role of these investigations in clinical practice. OBJECTIVES: To evaluate the sensitivity and specificity of the halo sign on temporal artery US, using the ACR 1990 classification as a reference standard, to investigate whether US could be used as triage for TAB. To compare the accuracy of US with TAB in the subset of paired studies that have obtained both tests on the same patients, to investigate whether it could replace TAB as one of the criteria in the ACR 1990 classification. SEARCH METHODS: We used standard Cochrane search methods for diagnostic accuracy. The date of the search was 13 September 2022. SELECTION CRITERIA: We included all participants with clinically suspected GCA who were investigated for the presence of the halo sign on temporal artery US, using the ACR 1990 criteria as a reference standard. We included studies with participants with a prior diagnosis of polymyalgia rheumatica. We excluded studies if participants had had two or more weeks of steroid treatment prior to the investigations. We also included any comparative test accuracy studies of the halo sign on temporal artery US versus TAB, with use of the 1990 ACR diagnostic criteria as a reference standard. Although we have chosen to use this classification for the purpose of the meta-analysis, we accept that it incorporates unavoidable incorporation bias, as TAB is itself one of the five criteria. This increases the specificity of TAB, making it difficult to compare with US. We excluded case-control studies, as they overestimate accuracy, as well as case series in which all participants had a prior diagnosis of GCA, as they can only address sensitivity and not specificity. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed the studies for inclusion in the review. They extracted data using a standardised data collection form and employed the QUADAS-2 tool to assess methodological quality. As not enough studies reported data at our prespecified halo threshold of 0.3 mm, we fitted hierarchical summary receiver operating characteristic (ROC) models to estimate US sensitivity and also to compare US with TAB. We graded the certainty of the evidence using the GRADE approach. MAIN RESULTS: Temporal artery ultrasound was investigated in 15 studies (617 participants with GCA out of 1479, 41.7%), with sample sizes ranging from 20 to 381 participants (median 69). There was wide variation in sensitivity with a median value of 0.78 (interquartile range (IQR) 0.45 to 0.83; range 0.03 to 1.00), while specificity was fair to good in most studies with a median value of 0.91 (IQR 0.78 to 1.00; range 0.40 to 1.00) and four studies with a specificity of 1.00. The hierarchical summary receiver operating characteristic (HSROC) estimate of sensitivity (95% confidence interval (CI)) at the high specificity of 0.95 was 0.51 (0.21 to 0.81), and 0.84 (0.58 to 0.95) at 0.80 specificity. We considered the evidence on sensitivity and specificity as of very low certainty due to risk of bias (-1), imprecision (-1), and inconsistency (-1). Only four studies reported data at a halo cut-off > 0.3 mm, finding the following sensitivities and specificities (95% CI): 0.80 (0.56 to 0.94) and 0.94 (0.81 to 0.99) in 55 participants; 0.10 (0.00 to 0.45) and 1.00 (0.84 to 1.00) in 31 participants; 0.73 (0.54 to 0.88) and 1.00 (0.93 to 1.00) in 82 participants; 0.83 (0.63 to 0.95) and 0.72 (0.64 to 0.79) in 182 participants. Data on a direct comparison of temporal artery US with biopsy were obtained from 11 studies (808 participants; 460 with GCA, 56.9%). The sensitivity of US ranged between 0.03 and 1.00 with a median of 0.75, while that of TAB ranged between 0.33 and 0.92 with a median of 0.73. The specificity was 1.00 in four studies for US and in seven for TAB. At high specificity (0.95), the sensitivity of US and TAB were 0.50 (95% CI 0.24 to 0.76) versus 0.80 (95% CI 0.57 to 0.93), respectively, and at low specificity (0.80) they were 0.73 (95% CI 0.49 to 0.88) versus 0.92 (95% CI 0.69 to 0.98). We considered the comparative evidence on the sensitivity of US versus TAB to be of very low certainty because specificity was overestimated for TAB since it is one of the criteria used in the reference standard (-1), together with downgrade due to risk of bias (-1), imprecision (-1), and inconsistency (-1) for both sensitivity and specificity. AUTHORS' CONCLUSIONS: There is limited published evidence on the accuracy of temporal artery US for detecting GCA. Ultrasound seems to be moderately sensitive when the specificity is good, but data were heterogeneous across studies and either did not use the same halo thickness threshold or did not report it. We can draw no conclusions from accuracy studies on whether US can replace TAB for diagnosing GCA given the very low certainty of the evidence. Future research could consider using the 2016 revision of the ACR criteria as a reference standard, which will limit incorporation bias of TAB into the reference standard.

Temporal artery ultrasonography for the diagnosis of giant cell arteritis: a case report.

Orofacial pain is a worldwide pain problem, with many patients unable to find appropriate diagnosis and treatment. Orofacial pain includes pain arising from the odontogenic and nonodontogenic structures in the head and neck region. Dental clinicians need to have a thorough knowledge and skill to diagnose, manage, and treat patients with odontogenic pain or refer patients for treatment of nonodontogenic pain to specialists such as orofacial pain specialists, neurologists, otolaryngologists, and rheumatologists. More often, dental practitioners diagnose patients with a temporomandibular disorder (TMD), and when treatment is ineffective, term it "atypical facial pain." The first requirement for effective treatment is an accurate diagnosis. Dental clinicians must be aware of giant cell arteritis (GCA), a chronic large-vessel vasculitis, primarily affecting adults over the age of 50 years, as it frequently mimics and is misdiagnosed as TMD. GCA is associated with loss of vision, and stroke and can be a life-threatening disorder. Therefore, diagnostic testing for GCA and differential diagnosis should be common knowledge in the armamentarium of all dental clinicians. Historically, temporal artery biopsy was considered the definitive diagnostic test for GCA. Temporal artery ultrasound (TAUSG), a safe and noninvasive imaging modality, has replaced the previous diagnostic gold standard for GCA, the temporal artery biopsy, owing to its enhanced diagnostic capabilities and safety profile. The present case report describes a patient with GCA, and the role TAUSG played in the diagnosis. Case report: A 72-year-old woman presented with left-sided facial pain, jaw claudication, dysesthesia of the tongue, and episodic loss of vision of 2 years' duration. She was diagnosed with and treated for a myriad of dental conditions including endodontia and temporomandibular joint therapy with no benefit. A thorough history and physical examination, combined with serologic analysis, led to the diagnosis of GCA and TAUSG, which confirmed the diagnosis. Conclusion: This report underscores the responsibility of differential diagnosis and early recognition of GCA facilitated by TAUSG in optimizing treatment outcomes as a viable, noninvasive diagnostic tool. (Quintessence Int 2024;55:336-343; doi: 10.3290/j.qi.b4938419).

Eosinophilic giant cell arteritis: A different subset of disease?

OBJECTIVES: To describe the clinical findings, response to therapy and course of patients with transmural eosinophilic infiltration at temporal artery biopsy (TAB). METHODS: The study consisted of a retrospective cohort of 254 consecutive GCA patients with evidence of transmural inflammation at TAB seen at the Santa Maria Nuova Hospital over a 28-year period. The findings of the 22 patients with eosinophilic infiltration (≥ 20 eosinophils/hpf) at TAB were compared with those of 232 patients without. Among these 232 patients, we sampled 42 GCA patients matched for age, sex and follow-up duration to the 22 with eosinophilic infiltration, to compare allergic manifestations. RESULTS: GCA patients with eosinophilic infiltration compared to those without presented more frequently cranial symptoms (p = 0.052), headaches (p = 0.005), abnormalities of TAs at physical examination (p = 0.045), jaw claudication (p = 0.024), and systemic manifestations (p = 0.016) and had higher CRP levels at diagnosis (p = 0.001). Regarding histological lesions, a severe transmural inflammation, laminar necrosis and intraluminal acute thrombosis were more frequently observed in patients with eosinophilic infiltration (p = 0.066, p < 0.001, and p = 0.010, respectively). Long-term remission and flares were similar in the two groups. When 21 GCA patients with eosinophilic infiltration were compared to 42 without, blood eosinophilic counts at diagnosis were normal and no patients had evidence or developed allergic manifestations and/or clinical findings of systemic necrotizing vasculitis. CONCLUSION: Patients with transmural eosinophilic infiltration represent a subset of GCA with cranial disease and more severe inflammation.

Usefulness of 18F-FDG PET-CT for assessing large-vessel involvement in patients with suspected giant cell arteritis and negative temporal artery biopsy.

OBJECTIVE: To investigate the usefulness of 18F-FDG PET-CT for assessing large-vessel (LV) involvement in patients with suspected giant cell arteritis (GCA) and a negative temporal artery biopsy (TAB). METHODS: A retrospective review of our hospital databases was conducted to identify patients with suspected GCA and negative TAB who underwent an 18F-FDG PET-CT in an attempt to confirm the diagnosis. The gold standard for GCA diagnosis was clinical confirmation after a follow-up period of at least 12 months. RESULTS: Out of the 127 patients included in the study, 73 were diagnosed with GCA after a detailed review of their medical records. Of the 73 patients finally diagnosed with GCA, 18F-FDG PET-CT was considered positive in 61 cases (83.5%). Among the 54 patients without GCA, 18F-FDG PET-CT was considered positive in only eight cases (14.8%), which included 1 case of Erdheim-Chester disease, 3 cases of IgG4-related disease, 1 case of sarcoidosis, and 3 cases of isolated aortitis. Overall, the diagnostic performance of 18F-FDG PET-CT for assessing LV involvement in patients finally diagnosed with GCA and negative TAB yielded a sensitivity of 83.5%, specificity of 85.1%, and a diagnostic accuracy of 84% with an area under the ROC curve of 0.844 (95% CI: 0.752 to 0.936). The sensitivity was 89% in occult systemic GCA and 100% in extracranial LV-GCA. CONCLUSION: Our study confirms the utility of 18F-FDG PET-CT in patients presenting with suspected GCA and a negative TAB by demonstrating the presence of LV involvement across different subsets of the disease.