title: Posttreatment variables improve outcome prediction after intra-arterial therapy for acute ischemic stroke.
abstract: BACKGROUND
  There are multiple clinical and radiographic factors that influence outcomes after endovascular reperfusion therapy (ERT) in acute ischemic stroke (AIS). We sought to derive and validate an outcome prediction score for AIS patients undergoing ERT based on readily available pretreatment and posttreatment factors.
  
  
  METHODS
  The derivation cohort included 511 patients with anterior circulation AIS treated with ERT at 10 centers between September 2009 and July 2011. The prospective validation cohort included 223 patients with anterior circulation AIS treated in the North American Solitaire Acute Stroke registry. Multivariable logistic regression identified predictors of good outcome (modified Rankin score ≤2 at 3 months) in the derivation cohort; model β coefficients were used to assign points and calculate a risk score. Discrimination was tested using C statistics with 95% confidence intervals (CIs) in the derivation and validation cohorts. Calibration was assessed using the Hosmer-Lemeshow test and plots of observed to expected outcomes. We assessed the net reclassification improvement for the derived score compared to the Totaled Health Risks in Vascular Events (THRIVE) score. Subgroup analysis in patients with pretreatment Alberta Stroke Program Early CT Score (ASPECTS) and posttreatment final infarct volume measurements was also performed to identify whether these radiographic predictors improved the model compared to simpler models.
  
  
  RESULTS
  Good outcome was noted in 186 (36.4%) and 100 patients (44.8%) in the derivation and validation cohorts, respectively. Combining readily available pretreatment and posttreatment variables, we created a score (acronym: SNARL) based on the following parameters: symptomatic hemorrhage [2 points: none, hemorrhagic infarction (HI)1-2 or parenchymal hematoma (PH) type 1; 0 points: PH2], baseline National Institutes of Health Stroke Scale score (3 points: 0-10; 1 point: 11-20; 0 points: >20), age (2 points: <60 years; 1 point: 60-79 years; 0 points: >79 years), reperfusion (3 points: Thrombolysis In Cerebral Ischemia score 2b or 3) and location of clot (1 point: M2; 0 points: M1 or internal carotid artery). The SNARL score demonstrated good discrimination in the derivation (C statistic 0.79, 95% CI 0.75-0.83) and validation cohorts (C statistic 0.74, 95% CI 0.68-0.81) and was superior to the THRIVE score (derivation cohort: C statistic 0.65, 95% CI 0.60-0.70; validation cohort: C-statistic 0.59, 95% CI 0.52-0.67; p < 0.01 in both cohorts) but was inferior to a score that included age, ASPECTS, reperfusion status and final infarct volume (C statistic 0.86, 95% CI 0.82-0.91; p = 0.04). Compared with the THRIVE score, the SNARL score resulted in a net reclassification improvement of 34.8%.
  
  
  CONCLUSIONS
  Among AIS patients treated with ERT, pretreatment scores such as the THRIVE score provide only fair prognostic information. Inclusion of posttreatment variables such as reperfusion and symptomatic hemorrhage greatly influences outcome and results in improved outcome prediction.
authors.affiliation: Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Ill., USA.
authors.forename: Shyam
authors.initials: S
authors.lastname: Prabhakaran
authors.forename: Tudor G
authors.initials: TG
authors.lastname: Jovin
authors.forename: Ashis H
authors.initials: AH
authors.lastname: Tayal
authors.forename: Muhammad S
authors.initials: MS
authors.lastname: Hussain
authors.forename: Thanh N
authors.initials: TN
authors.lastname: Nguyen
authors.forename: Kevin N
authors.initials: KN
authors.lastname: Sheth
authors.forename: John B
authors.initials: JB
authors.lastname: Terry
authors.forename: Raul G
authors.initials: RG
authors.lastname: Nogueira
authors.forename: Anat
authors.initials: A
authors.lastname: Horev
authors.forename: Dheeraj
authors.initials: D
authors.lastname: Gandhi
authors.forename: Dolora
authors.initials: D
authors.lastname: Wisco
authors.forename: Brenda A
authors.initials: BA
authors.lastname: Glenn
authors.forename: Bryan
authors.initials: B
authors.lastname: Ludwig
authors.forename: Paul F
authors.initials: PF
authors.lastname: Clemmons
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Cronin
authors.forename: Melissa
authors.initials: M
authors.lastname: Tian
authors.forename: David
authors.initials: D
authors.lastname: Liebeskind
authors.forename: Osama O
authors.initials: OO
authors.lastname: Zaidat
authors.forename: Alicia C
authors.initials: AC
authors.lastname: Castonguay
authors.forename: Coleman
authors.initials: C
authors.lastname: Martin
authors.forename: Nils
authors.initials: N
authors.lastname: Mueller-Kronast
authors.forename: Joey D
authors.initials: JD
authors.lastname: English
authors.forename: Italo
authors.initials: I
authors.lastname: Linfante
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Malisch
authors.forename: Rishi
authors.initials: R
authors.lastname: Gupta
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000628:therapy*; D005260:Female; D005343:Fibrinolytic Agents / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015424:Reperfusion; D012720:Severity of Illness Index; D020521:Stroke / Q000628:therapy*; D015912:Thrombolytic Therapy / Q000379:methods; D010959:Tissue Plasminogen Activator / Q000627:therapeutic use; D016896:Treatment Outcome
chemical_list: D005343:Fibrinolytic Agents; D010959:Tissue Plasminogen Activator