Reliability and Utility of the Alberta Stroke Program Early Computed Tomography Score in Hyperacute Stroke
Introduction
Stroke interventions are time critical, and patients who present to the hospital within the first 60 minutes of onset have the greatest chance of benefitting from revascularization therapies.1 Thus, it has been clinically crucial to develop systems, tools, and technologies to optimize the number of patients receiving treatment earlier.2 For example, education in recognizing stroke symptoms, efficient code stroke methods, and the introduction of telemedicine have led to an increase in the proportion of stroke patients arriving at the hospital earlier.3 The preliminary implementation of mobile stroke units has allowed the use of pre-hospital treatment to reduce the median time from stroke onset to therapy decision to as little as 35 minutes.4 Currently, the Alberta Stroke Program Early Computed Tomography Score (ASPECTS) on non-contrast computed tomography (NCCT) represents a commonly used imaging tool for detecting early ischemic change (EIC). However, the use of ASPECTS is highly time dependent, with optimal detection on NCCT hours to days from stroke onset.5, 6, 7 As such, and with a shift to earlier stroke treatment times, it is currently unknown whether the utility of ASPECTS will persist as a simple and reliable method for assessing ischemic change.
Five randomized controlled trials demonstrated the superiority of intra-arterial and intravenous tissue plasminogen activator (IV-tPA) treatment over standard treatment for acute ischemic stroke patients with large artery occlusion.8, 9, 10, 11, 12 For most of these trials, the ASPECTS was used to grade the degree of EIC, allowing the prediction of irreversible ischemic injury.13 Similarly, for patients only eligible for IV-tPA, the ASPECTS on NCCT has proven a simple and reliable method to identify stroke patients unlikely to make an independent recovery despite this treatment.14, 15 Important advantages of ASPECTS on NCCT are its geographical and temporal ubiquity and its high sensitivity for the detection of intracerebral hemorrhage.14 EIC on NCCT is measured by a reduction in Hounsfield units (HU), which are time dependent. Parenchymal hypoattenuation is due to an increase in brain tissue water content as a result of ischemic injury, leading to ionic or vasogenic edema.16, 17 Thus, the visibility of ischemic change on NCCT varies from hours to days later depending on the magnitude of water uptake in ischemic tissues.5, 6, 7 As it is established that time affects the visibility of ischemic change, we hypothesized that the ASPECTS in hyperacute times is not a reliable measure for selecting patients for reperfusion therapies. Consequently, the objective of our study was to evaluate whether hyperacute time from ischemic stroke onset to initial NCCT influences the inter-rater variability and prognostic accuracy of ASPECTS for a 3-month functional outcome.
Section snippets
Study Population
This was a retrospective, single-center, cohort study of acute anterior circulation ischemic stroke patients admitted to the Royal Melbourne Hospital between December 26, 2007, and April 20, 2014, who received thrombolysis. Patients were excluded if baseline demographic or follow-up clinical data were unavailable during the patients' time in the ward or if a 3-month follow-up modified Rankin Scale (mRS) was unavailable. Patients were also excluded if the NCCT was severely movement degraded. The
Subject Characteristics
There were a total of 379 participants who met the inclusion criteria and were included in this single-center, retrospective, observational study. The median (interquartile range (IQR)) time of acute stroke onset to CT scan (OCT) was 100 (73-142) minutes. Thus, 100 minutes was used as the time point to define the earlier (≤100 minutes) and later time periods (>100 minutes) of OCT. Baseline characteristics were similar between time periods except for the higher NIHSS score in the early group
Discussion
This study has demonstrated that the NCCT ASPECTS in the early period after stroke is both more difficult to assess, as reflected in reduced inter-rater agreement, and less reliable for prognostication. This is a clinically important finding given the recommendation to use ASPECTS 6-10 as an eligibility criterion for thrombectomy in the recent American Heart Association guidelines update.19
When we assessed the prognostic accuracy of ASPECTS for a 3-month functional outcome, as measured by the
Conclusions
This study confirms that ASPECTS in earlier times (within 100 minutes) have greater inter-rater variability, but it has additionally demonstrated that the prognostic accuracy of ASPECTS is weaker in the early window. Extra care should be exercised in adopting the ASPECTS on NCCT to ultra-early times as a tool for selecting patients for revascularization. We propose further investigation and validation of the ASPECTS as well as the role of alternative imaging modalities in hyperacute stroke.
References (29)
- et al.
Streamlining of prehospital stroke management: the golden hour
Lancet Neurol
(2013) - et al.
Diagnosis and treatment of patients with stroke in a mobile stroke unit versus in hospital: a randomised controlled trial
Lancet Neurol
(2012) - et al.
Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy. ASPECTS Study Group. Alberta Stroke Programme Early CT Score
Lancet
(2000) - et al.
Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy
Lancet
(2000) - et al.
Brain oedema in focal ischaemia: molecular pathophysiology and theoretical implications
Lancet Neurol
(2007) - et al.
The “golden hour” and acute brain ischemia: presenting features and lytic therapy in >30,000 patients arriving within 60 minutes of stroke onset
Stroke
(2010) Time is brain—quantified
Stroke
(2006)- et al.
Can stroke physicians and neuroradiologists identify signs of early cerebral infarction on CT?
J Neurol Neurosurg Psychiatry
(1999) - et al.
Interobserver agreement in assessing early CT signs of middle cerebral artery infarction
AJNR Am J Neuroradiol
(1996) - et al.
Imaging-based decision making in thrombolytic therapy for ischemic stroke: present status
Stroke
(2003)
Stent-retriever thrombectomy after intravenous t-PA vs. t-PA alone in stroke
N Engl J Med
Thrombectomy within 8 hours after symptom onset in ischemic stroke
N Engl J Med
A randomized trial of intraarterial treatment for acute ischemic stroke
N Engl J Med
Randomized assessment of rapid endovascular treatment of ischemic stroke
N Engl J Med
Cited by (22)
Comparison of consistency in acute stroke: Automated ASPECT score software tools and manual consensus scores
2024, European Journal of RadiologyUpdate on imaging in Code Stroke
2023, RadiologiaAssociations between early ischemic signs on non-contrast CT and time since acute ischemic stroke onset: A scoping review
2022, European Journal of RadiologyCitation Excerpt :An often-used semi-quantitative grading method for the extent of hypodensity is the Alberta Stroke Program Early CT Score (ASPECTS) [40,41]. Visual assessment of hypodensity suffers from a low inter-observer agreement and low sensitivity, especially early since onset [40,42]. This is due to the subtlety of hypodensity in the first few hours since onset, and the significant uptake in water that has to occur before a change in HU can be visible by the human eye [43].
Assistance from Automated ASPECTS Software Improves Reader Performance
2021, Journal of Stroke and Cerebrovascular DiseasesCitation Excerpt :Defining the best reference standard for an ASPECTS study is challenging. Numerous studies have shown that expert readers often have suboptimal agreement with each other regarding the total score or the individual regions affected.8-13 To help improve the accuracy of the readers, we had 3 expert neuroradiologists review the CT scan along with a follow-up MRI scan that showed the final infarct.
Alberta Stroke Program Early CT Score Calculation Using the Deep Learning-Based Brain Hemisphere Comparison Algorithm
2021, Journal of Stroke and Cerebrovascular DiseasesCitation Excerpt :It is important to assess the extent of a region of stroke on brain imaging during the acute ischemic period to determine eligibility for reperfusion therapy. However, ASPECTS in the early period after stroke is difficult to assess because of subtle changes in an ischemic lesion, leading to reduced inter-rater agreement in human readers.29,30 RAPID-ASPECTS and human readers showed minimal agreement in the early period after stroke, although this was improved with time from stroke onset.20,21
Detection of ischemic changes on baseline multimodal computed tomography: expert reading vs. Brainomix and RAPID software
2020, Journal of Stroke and Cerebrovascular DiseasesCitation Excerpt :CT perfusion (CTP) has a potential to discriminate between irreversibly damaged tissue, infarct core, and tissue at risk of infarction, penumbra (11,12). It has been demonstrated that visual applying of ASPECTS into CTP parametric maps has a strong correlation with good clinical outcome (defined as modified Rankin scale/mRS 0-2), with a prognostic value greater than NCCT ASPECTS (13–16). All previous studies have shown the highest correlation of good clinical outcome with cerebral blood volume (CBV) ASPECTS (13–16).
- 1
These two authors contributed equally.