title: Etiological classifications of transient ischemic attacks: subtype classification by TOAST, CCS and ASCO--a pilot study.
abstract: BACKGROUND
  In patients with transient ischemic attacks (TIA), etiological classification systems are not well studied. The Trial of ORG 10172 in Acute Stroke Treatment (TOAST), the Causative Classification System (CCS), and the Atherosclerosis Small Vessel Disease Cardiac Source Other Cause (ASCO) classification may be useful to determine the underlying etiology. We aimed at testing the feasibility of each of the 3 systems. Furthermore, we studied and compared their prognostic usefulness.
  
  
  METHODS
  In a single-center TIA registry prospectively ascertained over 2 years, we applied 3 etiological classification systems. We compared the distribution of underlying etiologies, the rates of patients with determined versus undetermined etiology, and studied whether etiological subtyping distinguished TIA patients with versus without subsequent stroke or TIA within 3 months.
  
  
  RESULTS
  The 3 systems were applicable in all 248 patients. A determined etiology with the highest level of causality was assigned similarly often with TOAST (35.9%), CCS (34.3%), and ASCO (38.7%). However, the frequency of undetermined causes differed significantly between the classification systems and was lowest for ASCO (TOAST: 46.4%; CCS: 37.5%; ASCO: 18.5%; p < 0.001). In TOAST, CCS, and ASCO, cardioembolism (19.4/14.5/18.5%) was the most common etiology, followed by atherosclerosis (11.7/12.9/14.5%). At 3 months, 33 patients (13.3%, 95% confidence interval 9.3-18.2%) had recurrent cerebral ischemic events. These were strokes in 13 patients (5.2%; 95% confidence interval 2.8-8.8%) and TIAs in 20 patients (8.1%, 95% confidence interval 5.0-12.2%). Patients with a determined etiology (high level of causality) had higher rates of subsequent strokes than those without a determined etiology [TOAST: 6.7% (95% confidence interval 2.5-14.1%) vs. 4.4% (95% confidence interval 1.8-8.9%); CSS: 9.3% (95% confidence interval 4.1-17.5%) vs. 3.1% (95% confidence interval 1.0-7.1%); ASCO: 9.4% (95% confidence interval 4.4-17.1%) vs. 2.6% (95% confidence interval 0.7-6.6%)]. However, this difference was only significant in the ASCO classification (p = 0.036). Using ASCO, there was neither an increase in risk of subsequent stroke among patients with incomplete diagnostic workup (at least one subtype scored 9) compared with patients with adequate workup (no subtype scored 9), nor among patients with multiple causes compared with patients with a single cause.
  
  
  CONCLUSIONS
  In TIA patients, all etiological classification systems provided a similar distribution of underlying etiologies. The increase in stroke risk in TIA patients with determined versus undetermined etiology was most evident using the ASCO classification.
authors.affiliation: Stroke Unit and Department of Neurology, University Hospital Basel, Basel, Switzerland. mamort@uhbs.ch
authors.forename: Margareth
authors.initials: M
authors.lastname: Amort
authors.forename: Felix
authors.initials: F
authors.lastname: Fluri
authors.forename: Florian
authors.initials: F
authors.lastname: Weisskopf
authors.forename: Henrik
authors.initials: H
authors.lastname: Gensicke
authors.forename: Leo H
authors.initials: LH
authors.lastname: Bonati
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Lyrer
authors.forename: Stefan T
authors.initials: ST
authors.lastname: Engelter
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D050197:Atherosclerosis / Q000150:complications; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000145:classification / Q000175:diagnosis / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D020521:Stroke / Q000145:classification / Q000175:diagnosis / Q000209:etiology*