Predicting Outcome in Guillain-Barré Syndrome: International Validation of the Modified Erasmus GBS Outcome Score

Abstract

Background and objectives: The clinical course and outcome of the Guillain-Barré syndrome (GBS) are diverse and vary among regions. The modified Erasmus GBS Outcome Score (mEGOS), developed with data from Dutch patients, is a clinical model that predicts the risk of walking inability in patients with GBS. The study objective was to validate the mEGOS in the International GBS Outcome Study (IGOS) cohort and to improve its performance and region specificity.

Methods: We used prospective data from the first 1,500 patients included in IGOS, aged ≥6 years and unable to walk independently. We evaluated whether the mEGOS at entry and week 1 could predict the inability to walk unaided at 4 and 26 weeks in the full cohort and in regional subgroups, using 2 measures for model performance: (1) discrimination: area under the receiver operating characteristic curve (AUC) and (2) calibration: observed vs predicted probability of being unable to walk independently. To improve the model predictions, we recalibrated the model containing the overall mEGOS score, without changing the individual predictive factors. Finally, we assessed the predictive ability of the individual factors.

Results: For validation of mEGOS at entry, 809 patients were eligible (Europe/North America [n = 677], Asia [n = 76], other [n = 56]), and 671 for validation of mEGOS at week 1 (Europe/North America [n = 563], Asia [n = 65], other [n = 43]). AUC values were >0.7 in all regional subgroups. In the Europe/North America subgroup, observed outcomes were worse than predicted; in Asia, observed outcomes were better than predicted. Recalibration improved model accuracy and enabled the development of a region-specific version for Europe/North America (mEGOS-Eu/NA). Similar to the original mEGOS, severe limb weakness and higher age were the predominant predictors of poor outcome in the IGOS cohort.

Discussion: mEGOS is a validated tool to predict the inability to walk unaided at 4 and 26 weeks in patients with GBS, also in countries outside the Netherlands. We developed a region-specific version of mEGOS for patients from Europe/North America.

Classification of evidence: This study provides Class II evidence that the mEGOS accurately predicts the inability to walk unaided at 4 and 26 weeks in patients with GBS.

Trial registration information: NCT01582763.

Figure 1. Study Population

Eu/NA = Europe/North America; IGOS = International GBS Outcome Study; mEGOS = Modified Erasmus GBS Outcome Score; GBS-DS = Guillain-Barré syndrome disability score.

Figure 2. Mean Observed Probabilities of Poor Outcome vs Mean Predicted Risks Based on the Original mEGOS Model

(A) Mean observed and predicted risks based on the modified Erasmus GBS Outcome Score (mEGOS) at entry. (B) Mean observed and predicted risks based on the mEGOS at 1 week. mEGOS entry validation cohort: full IGOS cohort n = 809, Europe/North America n = 677, Asia n = 76; mEGOS week 1 validation cohort: full IGOS cohort n = 671, Europe/North America n = 563, Asia n = 65. Eu/NA = Europe/North America.

Figure 3. Predicted Proportion of Patients Unable to Walk Independently Based on Original and Recalibrated mEGOS

Predicted probabilities of not being able to walk independently at 4 weeks and 6 months based on the modified Erasmus GBS Outcome Score (mEGOS) at entry (A) and mEGOS at week 1 (B). Probability graphs are based on the original mEGOS model (red) and the recalibrated model for the Europe/North America subgroup (green). Dashed and gray areas around the curves represent the 95% confidence intervals. The top (red and green) graphs provide the probabilities of not being able to walk independently at 4 weeks, and the bottom (red and green) graphs provide probabilities at 6 months. The mEGOS model can be used in all patients with Guillain-Barré syndrome (GBS) and variants of GBS who have lost the ability to walk. The mEGOS score can be calculated based on the scoring system provided in Table 1. Based on the mEGOS score and Figure 3, the probability of being unable to walk independently at 4 weeks or 6 months can be deduced for an individual patient. For predictions with the mEGOS in European and North American patients with GBS, the probability of poor outcome can be determined using the probability graphs based on the recalibrated model (green lines). For predictions in patients with GBS from countries outside Europe and North America, the probability graphs based on the original mEGOS model can be used (red lines).

Figure 4. Observed vs Predicted (Pre- and Postrecalibration) Risks (%) of Poor Outcome per mEGOS Score Value for European and North American Patients With Guillain-Barré Syndrome

Observed and predicted (pre- and postrecalibration) risks (%) of poor outcome per modified Erasmus GBS Outcome Score (mEGOS) score value for the Europe/North America subgroup. (A) Observed and predicted risks for the mEGOS at entry, predicting outcome at 4 weeks; (B) for the mEGOS at entry, predicting outcome at 6 months; (C) for the mEGOS at week 1, for predicting outcome at 4 weeks; and (D), for the mEGOS at week 1, predicting outcome at 6 months.