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. 2003 Jan;34(1):200-2.
doi: 10.1161/01.str.0000047102.61863.e3.

Predicting outcome in ischemic stroke: external validation of predictive risk models

Karen C Johnston  1 , Alfred F Connors Jr, Douglas P Wagner, E Clarke Haley Jr
Affiliations

Predicting outcome in ischemic stroke: external validation of predictive risk models

Karen C Johnston et al. Stroke. 2003 Jan.

Abstract

Background: Six multivariable models predicting 3-month outcome of acute ischemic stroke have been developed and internally validated previously. The purpose of this study was to externally validate the previous models in an independent data set.

Summary of report: We predicted outcomes for 299 patients with ischemic stroke who received placebo in the National Institute of Neurological Disorders and Stroke rt-PA trial. The model equations used 6 acute clinical variables and head CT infarct volume at 1 week as independent variables and 3-month National Institutes of Health Stroke Scale, Barthel Index, and Glasgow Outcome Scale as dependent variables. Previously developed model equations were used to forecast excellent and devastating outcome for subjects in the placebo tissue plasminogen activator data set. Area under the receiver operator characteristic curve was used to measure discrimination, and calibration charts were used to measure calibration. The validation data set patients were more severely ill (National Institutes of Health Stroke Scale and infarct volume) than the model development subjects. Area under the receiver operator characteristic curves demonstrated remarkably little degradation in the validation data set and ranged from 0.75 to 0.89. Calibration curves showed fair to good calibration.

Conclusions: Our models have demonstrated excellent discrimination and acceptable calibration in an external data set. Development and validation of improved models using variables that are all available acutely are necessary.

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Figures

Figure
Figure
Calibration curves. The 6 calibration curves for the 6 models are shown. The solid 45° line reflects perfect calibration. Each model’s bias-corrected calibration is demonstrated by the observed line. In each case, the bias-corrected observed line deviates from the ideal line to some degree, but the observed line closely resembles the ideal line in 5 of the 6 models. NIH indicates National Institutes of Health Stroke Scale; BI, Barthel Index; GOS, Glasgow Outcome Scale.
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