Sensitivity and specificity of the hyperdense artery sign for arterial obstruction in acute ischemic stroke

Abstract

Background and purpose: In acute ischemic stroke, the hyperdense artery sign (HAS) on noncontrast computed tomography (CT) is thought to represent intraluminal thrombus and, therefore, is a surrogate of arterial obstruction. We sought to assess the accuracy of HAS as a marker of arterial obstruction by thrombus.

Methods: The Third International Stroke Trial (IST-3) was a randomized controlled trial testing the use of intravenous thrombolysis for acute ischemic stroke in patients who did not clearly meet the prevailing license criteria. Some participating IST-3 centers routinely performed CT or MR angiography at baseline. One reader assessed all relevant scans independently, blinded to all other data; we checked observer reliability. We combined IST-3 data with a systematic review and meta-analysis of all studies that assessed the accuracy of HAS using angiography (any modality).

Results: IST-3 had 273 patients with baseline CT or MR angiography and was the largest study of HAS accuracy. The meta-analysis (n=902+273=1175, including IST-3) found sensitivity and specificity of HAS for arterial obstruction on angiography to be 52% and 95%, respectively. HAS was more commonly identified in proximal than distal arteries (47% versus 37%; P=0.015), and its sensitivity increased with thinner CT slices (r=-0.73; P=0.001). Neither extent of obstruction nor time after stroke influenced HAS accuracy.

Conclusions: When present in acute ischemic stroke, HAS indicates a high likelihood of arterial obstruction, but its absence indicates only a 50/50 chance of normal arterial patency. Thin-slice CT improves sensitivity of HAS detection.

Clinical trial registration url: http://www.controlled-trials.com/ISRCTN25765518. Unique identifier: ISRCTN25765518.

Keywords: angiography; meta-analysis; stroke.

Figure 1

Systematic review data for the 16 selected articles and IST-3 Footnote: Data from individual studies was only included if at least sensitivity or specificity could be calculated. Unless stated otherwise, CT slice-thickness refers to the thickest slices used. CTA = CT angiography. MRA = MR angiography. HAS = Hyperdense Artery Sign. TP = True positive. TN = True negative. FP = False positive. FN = False negative. CI = Confidence Interval. * One patient had both a false positive HAS and a true occlusion without HAS (FN) in contralateral arteries; 39 results are therefore reported from 38 angiograms. † Data for proximal and distal middle cerebral artery are presented separately providing assessment of 200 arterial segments from 100 angiograms. ‡ Thin-slice CT data are presented. Thick-slice (5mm) data for the same angiography is also available.

Figure 2

Relationship between the sensitivity of a hyperdense artery sign (HAS) for arterial obstruction and non-contrast CT slice thickness Footnote: Closed dots represent IST-3 data (thin-slice ≤3mm, mean 1.65mm; thick-slice >3mm, mean 4.5mm). Open dots represent results from articles identified on systematic review. Two dots have been fractionally altered to reveal identical results (sensitivity = 0.27, slice thickness = 10mm). Correlation is r=−0.73, p=0.001.