Stroke subtype classification: A comparative study of ASCO and modified TOAST
Introduction
A reliable and precise etiologic classification is highly important in the treatment and prognostication of ischemic stroke. The modified TOAST (Trial of ORG 10172 in Acute Stroke Treatment) classification system for determining stroke etiologies [1] improved upon the criteria of the initial TOAST system in terms of reliability and accuracy [2]. However, even the modified TOAST is based on “the most likely cause(s) of stroke”, but ignores coexisting etiologies. In addition, patients with more than two stroke causes are still classified as “undetermined etiology”. Thus a good proportion of patients fall under the undetermined category, even though the potential causes of stroke are identifiable.
In the newer A–S–C–O (A for atherosclerosis, S for small vessel disease, C for cardiac source, O for other cause) Phenotypic System (ASCO) [3], every stroke patient's etiological pathology can be characterized, as well as acknowledgment made of the strength of the diagnostic evidence. Each of the four phenotypes (A, S, C, and O) is graded 1, 2, or 3, based on level of diagnostic certainty. In addition, the phenotype is given a grade of 0 if there is no evidence after thorough investigation, or a grade 9 if there was insufficient work-up to make a determination.
It may be presumed that application of the ASCO classification would reduce the proportion of patients with undetermined etiology from that determined by the modified TOAST. A previous study which compared TOAST and ASCO showed that ASCO grade 1 did not reduce the proportion of patients with undetermined cause [4]. We wanted to further test, in a larger study of first-time acute ischemic stroke patients, the hypothesis that the ASCO would result in a smaller proportion of patients with undetermined etiology than the modified TOAST method. We also aimed to test the extent of agreement between each etiologic subtype classified under ASCO vs. the modified TOAST.
Section snippets
Patients
We retrospectively analyzed data from 1375 ischemic stroke patients who were consecutively admitted to the Third Hospital of Hebei Medical University from 2007 to 2010. All the patients came from the Hebei region of China. Subsequently, we included only the first-time ischemic stroke patients from the 1375, based on the inclusion criteria. Demographic data and stroke risk factors such as age, gender, hypertension, diabetes mellitus, hyperlipidemia, current cigarette smoking, atrial fibrillation
Subject characteristics and risk factors
Of 1375 stroke patients, 425 with first-time stroke were recruited after excluding 948 with TIA, chronic cerebral infarction, recurrent stroke, or ischemic stroke associated with subarachnoid or parenchymal hemorrhage. The median age of the study population was 65 ± 18.0 years. Sixty percent of the patients were male and were younger than females (61.4 ± 0.79 vs. 67.6 ± 0.83; P < 0.001). The prevalence of hypertension, atrial fibrillation and coronary artery disease was significantly higher in the
Discussion
A stroke subtype classification should not only be accurate and reliable, but also precise in determining etiology. Under the modified TOAST criteria a good number of patients fall within the “undetermined cause” category. Our study, whose objective was to determine the amount of agreement between the modified TOAST and ASCO classifications, showed that the two systems are comparable except for the “undetermined” subtype. When ASCO 1 was compared with the modified TOAST, a reduction in the
Conclusion
Moderate to good agreement was found in every subtype category between the ASCO and improved TOAST classification systems. The characteristics of each system were useful in delineating etiology. The ASCO system was more accurate in identifying the etiology from available information, ASCO system provided a better phenotypic classification of stroke. However, most etiological diagnoses in both the classification systems are still based on clinical information and are thus presumptive.
Acknowledgment
We thank Medjaden Bioscience Limited for assisting in the preparation of this manuscript.
References (11)
- et al.
Classification of subtype of acute ischemic stroke definitions for use in a multicenter clinical trial
Stroke
(1993) - et al.
A new subtype classification of ischemic stroke based on treatment and etiologic
Eur Neurol
(2007) - et al.
New approach to stroke subtyping: the A–S–C–O (phenotypic) classification of stroke
Cerebrovasc Dis
(2009) - et al.
Stroke subtype classification to mechanism-specific and undetermined categories by TOAST, A–S–C–O, and causative classification system
Stroke
(2010) - et al.
International trends in stroke mortality: 1970–1985
Stroke
(1990)