Giant cell arteritis (GCA or temporal arteritis or cranial arteritis) or Horton disease is a vasculitis that occurs in older adults, affecting vessels of medium and large caliber. The diagnosis of GCA is a challenge for general practitioners and specialists. Since 1970, it is based on a combination of clinical, biological and histological signs. Temporal artery biopsy (TAB) was the reference method until recently. However, TAB has many drawbacks. Therefore, researches of the past 20 years have been intended to develop alternative diagnostic methods. This was notably the case of the color Doppler ultrasound (CDU) since the description by Wolfgang Schmidt of the halo sign. Although European and British recommendations put CDU as second line method, many authors suggest the possibility to do without TAB in many cases. In addition, many practitioners believe that it is not "ethical" to use an invasive unprofitable procedure like TAB, and have already been using CDU in their routine practice. However, no diagnostic algorithm validating this approach in a prospective series has been published to date. Therefore, the present study aim at validating a diagnostic algorithm of giant cell arteritis using color Doppler imaging of temporal arteries and cervicocephalic axes as first screening method.

Inclusion Criteria:

• ≥ 50 years
• C reactive protein (CRP) above normal
• Suspected of GCA according to clinician expertise and / or aortitis arteritis or of one or more arteries from the aorta imaging (CT angiography, magnetic resonance angiography or positron emission tomography TDM18FDG)
• Benefiting from Social Security or receiving it via a third party
• have given their participation agreement by understanding and accepting the constraints of the study

Exclusion Criteria:

• Received corticosteroid dose ≥ 20 mg of prednisone equivalent for more than 7 days in the month before inclusion
• Underwent temporal artery biopsy before color Doppler ultrasound
• History of GCA
• Terminal palliative phase or suffering from a disease or comorbidities such as life is involved in less than a year
• Patient with severe cognitive impairment
• Patient that can not be followed by the investigator for the duration of the study
• Refusal to participate in the study
• With enhanced protection (namely those deprived of liberty by a court or administrative order, patient staying in a health or social institution, under legal protection, and patients in emergencies)
• Pregnant or breastfeeding women, women of childbearing age who do not have effective contraception
• Participating in another clinical trial.

Two years after inclusion

This study concern patients with high clinical suspicion of GCA defined by 2 mandatory criteria that were age >50 and biological inflammatory syndrome with C-Reactive Protein elevation, and at least one of the following factors: abnormal temporal arteries, scalp hyperesthesia, jaw claudication, vision loss, pain in the shoulder girdle or pelvic girdle, unusual headache, impaired general condition, fever, or imaging positive result and absence of obvious differential diagnosis.