THU0542 THE IMPACT OF GLUCOCORTICOID INITIATION ON THE DIAGNOSTIC ACCURACY OF ULTRASOUND IN GIANT CELL ARTERITIS: EXPERIENCES FROM A DISTRICT GENERAL HOSPITAL IN THE UK
Authors: J. T. Sze, J. Dawson
Journal: Annals of the Rheumatic Diseases (2020)

Background: Temporal and axillary artery ultrasound (US) has been recommended by EULAR as the first-line investigation in patients with suspected giant cell arteritis (GCA). 1 US is reported as having a 77% sensitivity and 96% specificity for GCA. 1 However, these figures have largely been derived from studies carried out in specialist centres where US was performed rapidly following the onset of symptoms. When performed by highly experienced sonographers, halos can still be detected on US weeks after initiation of glucocorticoid treatment. 2 Little is known about the relationship between the dose and duration of glucocorticoid and diagnostic accuracy of US in real-world experience. Objectives: We evaluated the impact of glucocorticoid initiation on the diagnostic accuracy of US in patients with suspected GCA in routine clinical practice in a district general hospital. Methods: This is a single-centre retrospective study of all temporal and axillary artery US performed since its inception in November 2015 until October 2019. Patients who were aged ≥50 years and assessed by a rheumatologist were included in the study. US was performed by either a musculoskeletal consultant radiologist, musculoskeletal sonographer or vascular sonographer. US was considered positive for GCA when a halo, occlusion or stenosis was seen. Patients’ medical records and investigation results were reviewed in a systematic manner. The reference standard for GCA was the final clinical diagnosis after a minimum of 3-month rheumatology follow up. Results: 311 US performed on 305 patients were included. 62% of the scans were requested by rheumatologists, the rest by ophthalmologists and general physicians. 57 of these episodes had a final clinical diagnosis of GCA. US had an overall sensitivity of 39% and specificity of 100% for GCA. Overall positive and negative predictive values were 100% and 88%, respectively. Sensitivity was 31% for US done in the first 2 years (n=160) which was lower than sensitivity of 45% in the latter 2 years (n=151) ( p =0.2663). Specificity remained the same in the two periods. When performed on patients who were not on any glucocorticoids, US had a sensitivity of 89% which was significantly higher than sensitivity of 29% in those who had been treated with any dose or duration of steroids ( p =0.0007). Compared to US-negative GCA patients, US-positive GCA patients are older and more likely to have jaw claudication (Table 1). Table. Characteristics of patients with a final clinical diagnosis of GCA All GCA (n=57) US positive (n=22) US negative (n=35) p -value Age, mean years 74 78 72 0.01 Sex, no of females 41 (72%) 13 (59%) 27 (77%) 0.15 Any head pain present, no of patients 49 (86%) 18 (82%) 31 (89%) 0.50 Jaw claudication, no of patients 26 (46%) 15 (68%) 14 (40%) 0.04 Ocular ischaemia, no of patients 8 (14%) 3 (14%) 5 (14%) 0.94 ESR, mm/hour,* mean 67 66 68 0.78 CRP, mg/L,* mean 85 85 84 0.96 Days of high-dose glucocorticoid pre-US, mean 5 4 6 0.11 * ESR was determined in n=55 patients and CRP in n=53 patients. ESR and CRP were measured before initiation of high-dose steroid treatment. Table 2. Diagnostic accuracy of US stratified by duration of high dose glucocorticoid* pre-scan Steroid duration n Sensitivity, % Specificity, % PPV, % NPV, % 0-1 day 154 71 100 100 97 2-3 days 34 † 22 100 100 77 4-5 days 32 † 33 100 100 79 6-7 days 18 13 100 100 59 &gt;7 days 41 33 100 100 72 *&gt;30mg of oral prednisone or equivalent †included episodes when patients were treated with intravenous methylprednisone Conclusion: US has an 89% sensitivity and 100% specificity for GCA when performed before initiation of glucocorticoid. Its sensitivity rapidly decreases within a day of starting high dose steroid but up to one-third of GCA cases can still be detected after over 1 week of treatment. References: [1]Dejaco C, Ramiro S, Duftner C, et al . EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice. Ann Rheum Dis 2018;77:636-43. [2]De Miguel E, Roxo A, Castillo C, et al . The utility and sensitivity of colour Doppler ultrasound in monitoring changes in giant cell arteritis. Clin Exp Rheumatol 2012;30:S34-8. Disclosure of Interests None declared