Predicting Mortality and Functional Outcomes after Ischemic Stroke: External Validation of a Prognostic Model

Accurate prediction of outcomes after stroke is important, particularly if the predictive model can be applied to patient care and to relaying information to patients and families. Prediction of functional outcomes after ischemic stroke is challenging. There are a plethora of stroke-related clinical and imaging data to consider.

The authors previously derived predictive models for 3-month mortality and 3-month modified Rankin Score (mRS) score after acute ischemic stroke utilizing a cohort of patients from 1999. The purpose of the current study was to test the validity of those models. And two independent data sets from 2005 and 2010 that include comprehensive outcome measurements in a well-characterized cohort of ischemic strokes were used to assess external validity by utilizing measures of agreement between predicted and observed values, calibration, and discrimination using Transparent Reporting of a multivariable prediction model for Individual Prognosis or Diagnosis.

The results showed that the 3-month mortality model performed well in the validation datasets with an average prediction error (Brier score) of 0.045 for 2005 and 0.053 for 2010 and excellent discrimination with an area under the curve of 0.86 (95% CI: 0.79, 0.93) for 2005 and 0.84 (0.76, 0.92) for 2010. Predicted 3-month mRS also performed well in the validation datasets with R2 of 0.57 for 2005 and 0.50 for 2010 and a root mean square error of 0.85 for 2005 and 1.05 for 2010. Predicted mRS tended to be higher than actual in both validation datasets. Re-estimation of the model parameters for age and severe white matter hyperintensity in both 2005 and 2010 and for diabetes in 2005 improved predictive accuracy. 

In conclusion, the models accurately predict 3-month mortality and functional outcome in two independent study cohorts with minor re-calibration. These models provide insight into post stroke recovery and may have utility in counseling patients and their families as well as for designing clinical trials and in epidemiological research.  

Article by Achala Vagal, et al, from USA.

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