Stroke subtype classification: A comparative study of ASCO and modified TOAST

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Abstract

Background and purpose

The ASCO stroke classification may be an improvement over the modified TOAST for etiological diagnoses. We aimed to compare the differences in stroke subtype classification between these two classification system.

Methods

Selected for this study were 425 first-time acute ischemic stroke patients. For each, the cause of ischemic stroke was classified according to both the ASCO and modified TOAST criteria. The κ statistic and McNemar test were used to compare the similarities and differences, respectively, between the two approaches.

Results

More patients were classified as having an atherosclerotic etiology under the ASCO 1 category than the modified TOAST system (60.2% vs. 57.9%; P = 0.132). There was no significant difference between the proportion of patients with undetermined etiology as defined by the ASCO 1 and the modified TOAST (15.5% vs. 16.2%; P = 0.795). Both the modified TOAST and ASCO-1 correctly identified all patients with etiology “other cause”. Agreement between the two classification systems was high in every subtype category except ‛undetermined’ (κ > 0.81 for atherosclerosis, κ = 0.61 to κ = 0.8 for cardiac disease, and κ = 0.480 for undetermined). When ASCO-1 to ASCO 3 were applied, atherosclerosis was identified as the cause in 76.0% of patients, small artery disease in 46.4%, and cardiac disease in 11.3%.

Conclusion

There is a moderately high agreement between the ASCO and modified TOAST classification schemes in all subtypes except that of “undetermined” etiology. Application of ASCO-1 did not reduce the proportion of patients ‘undetermined’ etiology compared to 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.

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