External Validation of the Early Prediction of Functional Outcome After Stroke Prediction Model for Independent Gait at 3 Months After Stroke

Abstract

IntroductionThe Early Prediction of Functional Outcome after Stroke (EPOS) model for independent gait is a tool to predict between days 2 and 9 poststroke whether patients will regain independent gait 6 months after stroke. External validation of the model is important to determine its clinical applicability and generalizability by testing its performance in an independent cohort. Therefore, this study aimed to perform a temporal and geographical external validation of the EPOS prediction model for independent gait after stroke but with the endpoint being 3 months instead of the original 6 months poststroke.MethodsTwo prospective longitudinal cohort studies consisting of patients with first-ever stroke admitted to a Swiss hospital stroke unit. Sitting balance and strength of the paretic leg were tested at days 1 and 8 post-stroke in Cohort I and at days 3 and 9 in Cohort II. Independent gait was assessed 3 months after symptom onset. The performance of the model in terms of discrimination (area under the receiver operator characteristic (ROC) curve; AUC), classification, and calibration was assessed.ResultsIn Cohort I [N = 39, median age: 74 years, 33% women, median National Institutes of Health Stroke Scale (NIHSS) 9], the AUC (95% confidence interval (CI)] was 0.675 (0.510, 0.841) on day 1 and 0.921 (0.811, 1.000) on day 8. For Cohort II (N = 78, median age: 69 years, 37% women, median NIHSS 8), this was 0.801 (0.684, 0.918) on day 3 and 0.846 (0.741, 0.951) on day 9.Discussion and ConclusionExternal validation of the EPOS prediction model for independent gait 3 months after stroke resulted in an acceptable performance from day 3 onward in mild-to-moderately affected patients with first-ever stroke without severe prestroke disability. The impact of applying this model in clinical practice should be investigated within this subgroup of patients with stroke. To improve the generalizability of patients with recurrent stroke and those with more severe, neurological comorbidities, the performance of the EPOS model within these patients should be determined across different geographical areas.

Predicting Recovery of Independent Walking After Stroke

“…In the development study, 5 they found that the TCT-3 and the MI leg score on the ninth day could predict independent walking at 6 mos poststroke with 92% accuracy. However, as expected, these values decreased in the validation cohort 36 : TCT-3 and the MI leg score on the ninth day poststroke, could predict independent walking at 3 mos after stroke with 86% accuracy (overall accuracy = 0.86, sensitivity = 0.93, specificity = 0.65).…”

“…Moreover, Veerbeek et al 36 recently published an article about the external validation of their EPOS study. An important difference with the development study of 2011 was that the outcome of interest was measured 3 mos after stroke (subacute phase) instead of 6 mos after stroke (chronic phase).…”

“…However, their model is not validated yet, causing difficulty in concluding which prognostic model is best in predicting independent walking after stroke. Veerbeek 37 proposed to validate the TWIST model of Smith et al 34 in the upcoming years. Validation of the TWIST model will result in insight in the actual accuracy of their model, which positively contributes to the comparison between the prognostic models with excellent accuracy and easy applicability.…”