Sonography in giant-cell arteritis

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.

New developments in giant cell arteritis

Giant cell arteritis (GCA) is a medium-to-large vessel vasculitis with potentially sight- and life- threatening complications. Our understanding of the pathogenesis, diagnosis, and treatment of GCA has advanced rapidly in recent times. The validity of using the American College of Rheumatology guidelines for diagnosis of GCA in a clinical setting has been robustly challenged. Erythrocyte sedimentation rate, an important marker of inflammation, is lowered by the use of statins and nonsteroidal anti-inflammatory drugs. Conversely, it may be falsely elevated with a low hematocrit. Despite the emergence of new diagnostic modalities, temporal artery biopsy remains the gold standard. Evidence suggests that shorter biopsy lengths and biopsies done weeks to months after initiation of steroid therapy are still useful. New imaging techniques such as positron emission tomography have shown that vascular inflammation in GCA is more widespread than originally thought. GCA, Takayasu arteritis, and polymyalgia rheumatica are no longer thought to exist as distinct entities and are more likely parts of a spectrum of disease. A range of immunosuppressive drugs have been used in conjunction with corticosteroids to treat GCA. In particular, interleukin-6 inhibitors are showing promise as a therapy.

Giant cell arteritis

Giant cell arteritis (GCA) is an immune-mediated vasculitis, affecting medium- to large-sized arteries, in individuals over the age of 50 years. Visual loss is a frequent complication of GCA, and once it occurs it tends to be both permanent and profound. Although major advances have been made in recent years in genetics, molecular biology and the description of the vessel wall morphology, the aetiology and pathogenesis of GCA are still incompletely understood. Over the years there has been much debate over whether polymyalgia rheumatica and GCA are separate or linked entities. Recent investigations support that polymyalgia rheumatica and GCA are two different expressions of the same underlying vasculitic disorder. A single cause or aetiological agent has not as yet been identified. Except for the histopathology of the arterial wall, there are no laboratory findings specific for GCA, and no particular signs or symptoms specific for the diagnosis. GCA typically causes vasculitis of the extracranial branches of the aorta and spares intracranial vessels. Transmural inflammation of the arteries induces luminal occlusion through intimal hyperplasia. Clinical symptoms reflect end-organ ischaemia. Branches of the external and internal carotid arteries are particularly susceptible. Corticosteroids remain the only proven treatment for GCA, the regimen initially involving high doses followed by a slow taper. However, early detection and treatment with high-dose corticosteroids is effective in preventing visual deterioration in most patients.

Giant cell (temporal) arteritis: an overview and update

Giant cell arteritis is a systemic disease that continues to be a sight-threatening medical emergency requiring prompt recognition and treatment in order to avoid devastating ophthalmic consequences. Although there have been advances in the genetic and immunologic understanding of the underlying pathogenesis of the disease, the exact etiology of the condition, to date, remains unclear. Visual manifestations of giant cell arteritis are the common mode of presentation, making the ophthalmologist critically responsible for early diagnosis and treatment. Although temporal artery biopsy remains the only confirmatory procedure, newer laboratory investigations and blood flow studies with fundus fluorescein angiography have aided in the diagnosis of temporal giant cell arteritis. Maintenance of a high index of clinical suspicion is essential to institute prompt adequate treatment, especially in atypical cases. Corticosteroids remain the mainstay of treatment of giant cell arteritis. Recently, immunosuppressive agents as secondary steroid-sparing drugs have been used, particularly in some steroid-resistant cases. A wider recognition of the disease will minimize the prevalence of irreversible visual loss among patients with giant cell arteritis.

The use of ultrasound as an aid in the diagnosis of giant cell arteritis: a pilot study comparing histological features with ultrasound findings

AIMS

We present our preliminary experience with the use of ultrasound in aiding the diagnosis of giant cell arteritis (GCA). Schmidt et al have previously described a hypoechoic or "halo" effect surrounding the walls of affected arteries on examination with ultrasound. We illustrate these features and explore the attributes and limitations of this technique.

METHOD

Two groups of patients were recruited: (1) patients with suspected GCA awaiting temporal artery biopsy and (2) patients with no history or symptoms of GCA of a similar age group. All the recruited patients underwent ultrasound examination of both temporal arteries. The findings on ultrasound were compared with the results of the histological specimens in group 1. For this study, the histological findings alone were used to define if a patient was suffering from GCA. No biopsies were taken in the patients in group 2.

RESULTS

Out of 26 patients with suspected GCA, seven patients were found to be positive on biopsy, of which six had been identified on ultrasound. Six patients were found to be false positive on ultrasound, but all had moderate-to-severe features of arteriosclerosis on histology. A total of 13 patients were found to be negative on ultrasound and negative on biopsy for GCA, two of these patients had histological features of arteriosclerosis. In the group with no symptoms of GCA (12 patients), in two patients hypoechoic areas were detected. The results presented give a sensitivity of 86%, specificity of 68%, and positive predictive value of 50% for the use of ultrasound in the diagnosis of GCA.

CONCLUSIONS

This preliminary study indicates that this test may be helpful in those patients with symptoms suggestive of GCA, but currently we cannot recommend any change of present practice.

Overview and report on international registry of sarcoid arthritis in childhood

Interest in childhood sarcoidosis prompted the formation of an international registry in 1991. Over the next 5 years, 53 patients were registered by 23 physicians from 14 countries. All the patients had definite histologic evidence of sarcoidosis: noncaseating granulomas of the skin (31), synovium (15), liver (10), lymph node (eight), lung (five), muscle (four), conjunctiva (three), or kidney (one). All but nine patients developed polyarthritis; 38 of 44 had persistent arthritis. Of those with persistent polyarthritis, arthritis occurred at presentation in 16 of 38 patients and inflammation of the uveal tract of the eye occurred in 44 with involvement of both anterior and posterior segments in 21. One patient was blind at the time of the report. Other ocular complications included chorioretinitis, glaucoma, and phthisis bulbi. Laboratory abnormalities included mild anemia and elevated erythrocyte sedimentation rate (39 out of 45). Angiotensin converting enzyme levels were elevated in 14 out of 37 patients. Information on these patients with sarcoidosis helps develop a better understanding of this rare childhood disease. These patients are discussed in conjunction with an overview of sarcoid arthropathy.

Central nervous system vasculitis

Central nervous system vasculitis occurs in a variety of clinical settings. Some exhibit a distinct age preference; others a tissue tropism. Most frequently encountered are giant cell arteritis (temporal arteritis) and vasculitis secondary to infections. The central nervous system may be involved in the antineutrophil cytoplasmic antibody-associated systemic vasculitides and occasionally neurologic abnormalities appear as a presenting manifestation of disease. Isolated angiitis of the central nervous system, a rare form of vasculitis that is restricted to the central nervous system, must be distinguished from other causes of central nervous system inflammation and from noninflammatory vascular disease. We are learning a great deal about the cellular mechanisms of vascular inflammation in general. Some manifestations of the clinical disease result from histologic features of the infiltrate and the size of affected vessel. However, the local consequences of inflammation, such as increased coagulation and altered vasomotor tone, as well as the systemic consequences, such as activation of the central noradrenergic systems, trigeminovascular system, and hypothalamic pituitary adrenal axis, contribute both to pathogenesis of disease and to recovery.