Evolution of ultrasound in giant cell arteritis

Abstract

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.

Diagnostic Modalities in Giant Cell Arteritis

“…1,33 In general, color Doppler ultrasound imaging protocols should include at least the superficial temporal arteries and the axillary arteries. 34 In the TABUL study, the halo sign had a sensitivity of 93% (vs. 91% sensitivity of TAB) and a specificity of 77% (vs. 81% specificity of TAB). 3,7 In one study, the finding of bilateral temporal artery halo signs led to a specificity of 100%.…”

“…Color Doppler ultrasound demonstrates characteristic signs suggestive of GCA, such as the hypoechoic and circumferential halo sign that corresponds to increased intima-media thickness from vessel wall edema, inflammatory cells, and myofibroblasts 1,33. In general, color Doppler ultrasound imaging protocols should include at least the superficial temporal arteries and the axillary arteries 34. In the TABUL study, the halo sign had a sensitivity of 93% (vs. 91% sensitivity of TAB) and a specificity of 77% (vs. 81% specificity of TAB) 3,7.…”

Giant Cell Arteritis in an Elderly Female With Pulmonary Tuberculosis

“…TAB has a lot of issues while evaluating possible GCA instances. In addition to being expensive and invasive, it has frequently been demonstrated to have a false-negative rate of up to 60%, most likely as a result of insufficient sample, skip lesions, and pre-operative steroid use [5,6]. A positive Halo sign on TAUS can be used to confirm a diagnosis of GCA in the presence of a high pre-test likelihood without the need for additional testing [6].…”

“…In addition to being expensive and invasive, it has frequently been demonstrated to have a false-negative rate of up to 60%, most likely as a result of insufficient sample, skip lesions, and pre-operative steroid use [5,6]. A positive Halo sign on TAUS can be used to confirm a diagnosis of GCA in the presence of a high pre-test likelihood without the need for additional testing [6]. With the added advantages of better access and lower relative cost, it performs as well as MRI and PET/CT while being more sensitive and cost-effective than TAB.…”

“…Another major advantage of TAUS over TAB is the time taken for reporting which can be up to 14 days for TAB. The use of TAUS may help in early detection of disease and prevention of permanent visual loss by prompt initiation of glucocorticoids [5,6].…”