OP0288 IMPACT OF CARDIOVASCULAR RISK ON THE DIAGNOSTIC ACCURACY OF THE ULTRASOUND HALO SCORE FOR GIANT CELL ARTERITIS

Abstract

BackgroundThe ultrasonographic (US) Halo Score provide a quantitative measure of the extent of vascular inflammation in patients with giant cell arteritis (GCA). High Halo Scores correlate with systemic markers of inflammation, rate of ocular ischaemia and may help to firmly diagnose GCA with high specificity. However, an increase in the intima media thickness (IMT) in patients with elevated cardiovascular risk (CVR) may lead to false-positive US findings.ObjectivesOur aim is to evaluate the impact of CVR on the diagnostic accuracy of the US Halo Score in patients with suspected GCA.MethodsThis is a retrospective observational study of patients suspected of having GCA and referred to our US fast track clinic. All patients underwent US exam within 24 hours per protocol. The IMT was measured in gray scale mode in cranial and extra-cranial (carotid, subclavian and axillary) arteries and the Halo Score was also determined to assess the extent of vascular inflammation. GCA diagnosis was confirmed after 6-month follow-up by the referring clinician. The European Society of Cardiology (ESC) Guidelines on CV Disease Prevention in clinical practice were used to define different categories of CVR. Patients were classified as very high, high, moderate or low CVR according to the Systemic Coronary Risk Evaluation (SCORE) obtained using the ESC CVD Risk Calculator app for mobile devices. Comparison between groups was performed and the diagnostic accuracy of the Halo Score in patients according to CVR was evaluated using ROC curves.ResultsOf the 157 patients referred to our US fast track clinic (67.5% female, mean age 73.7 years), 47(29.9%) had GCA confirmed after 6-month follow-up. There were no differences in CVR between patients with and without GCA (mean SCORE 20.6[21.6] vs 18.7[21];p=0.601). Among patients without GCA, extra-cranial artery IMT was significantly higher in patients with high/very high CVR than in those with low/moderate CVR (Table 1). The Halo Score was significantly higher in patients with high/very high CVR in non-GCA patients (9.38 (5.93) vs 6.16 (5.22);p=0.007). The area under the ROC curve of the Halo Score to identify GCA was 0.835 (CI95% 0.756-0.914), slightly greater in patients with low/moderate CVR (0.965 [CI95% 0.911-1]) versus patients with high/very high CVR (0.798[CI95% 0.702-0.895]) (Figure 1). A statistically weak positive correlation was found between the Halo Score and the SCORE (r 0.245;p=0.002).Table 1.Measurements of IMT in cranial and extracranial arteries and Halo Score values according to CVRArtery IMT mm, mean (SD)Patients with GCA n=47Patients without GCA n=110Patients with high/very high CVR n=37(78.7%)Patients with low/moderate CVR n=10(21.3%)pPatients with high/very high CVR n=79(71.8%)Patients with low/moderate CVR n=31(28.2%)pSuperficial temporal artery (both)0.66(0.25)0.45(0.11)0.0250.35(0.09)0.32(0.07)0.354Frontal branch (both)0.42(0.18)0.31(0.15)0.0560.26(0.05)0.26(0.06)0.577Parietal branch (both)0.43(0.17)0.35(0.12)0.1020.27(0.04)0.28(0.08)0.173Carotid artery (both)0.88(0.21)1.2(0.6)<0.0010.83(0.16)0.74(0.13)<0.001Subclavian artery (both)0.86(0.31)1.2(0.5)0.0010.74(0.18)0.6(0.13)<0.001Axillary artery (both)0.92(0.38)1.22(0.73)0.0210.72(0.16)0.59(0.15)<0.001Halo Score, mean (SD)18.5(8.8)17.2(10.6)0.699.38(5.93)6.16(5.22)0.007Figure 1.Diagnostic accuracy of the Halo Score for a clinical diagnosis of GCA after 6-month follow-up in (A) all GCA suspected patients, (B) patients with high/very high CVR and (C) patients with low/moderate CVRConclusionHigh CVR may influence the diagnostic accuracy of the US Halo Score leading to false-positive findings in these patients. Higher IMT values may be found in extracranial arteries of subjects with high/very high CVR without GCA. Thus, CVR should be taken into consideration in the US vascular assessment of patients with suspected GCA. These results need to be confirmed in larger cohorts to develop a modified US Halo Score applicable to patients with high CVR.Disclosure of InterestsNone declared