International Validation of the Erasmus Guillain-Barré Syndrome Respiratory Insufficiency Score

Abstract

Objective: This study aimed to validate the Erasmus Guillain-Barré Syndrome Respiratory Insufficiency Score in the International Guillain-Barré Syndrome Outcome Study cohort, and to improve its performance and region-specificity.

Methods: We examined data from the first 1,500 included patients, aged ≥6 years and not ventilated prior to study entry. Patients with a clinical variant or mild symptoms were also included. Outcome was mechanical ventilation within the first week from study entry. Model performance was assessed regarding the discriminative ability (area under the receiver operating characteristic curve) and the calibration (observed vs predicted probability of mechanical ventilation), in the full cohort and in Europe/North America and Asia separately. We recalibrated the model to improve its performance and region-specificity.

Results: In the group of 1,023 eligible patients (Europe/North America n = 842, Asia n = 104, other n = 77), 104 (10%) required mechanical ventilation within the first week from study entry. Area under the curve values were ≥0.80 for all validation subgroups. Mean observed proportions of mechanical ventilation were lower than predicted risks: full cohort 10% versus 21%, Europe/North America 9% versus 21%, and Asia 17% versus 23%. After recalibration, predicted risks for the full cohort and Europe/North America corresponded to observed proportions.

Interpretation: This prospective, international cohort study validated the Erasmus Guillain-Barré Syndrome Respiratory Insufficiency Score, and showed that the model can be used in the full spectrum of Guillain-Barré syndrome patients. In addition, a more accurate, region-specific version of the model was developed for patients from Europe/North America. ANN NEUROL 2022;91:521-531.

FIGURE 1

Study population. The sum of the exclusions in the second and third box is higher than the total number of exclusions at the corresponding step because of overlap in patient characteristics; that is, 6 patients with age < 6 years were included in Bangladesh, 5 patients who were ventilated prior to study entry were also admitted before the onset of weakness, and 1 patient with missing start date of mechanical ventilation was also admitted before the onset of weakness. EGRIS = Erasmus Guillain–Barré Syndrome Respiratory Insufficiency Score; Eu/NA = Europe/North America; IGOS = International Guillain–Barré Syndrome Outcome Study; val. = validation.

FIGURE 2

Discrimination upon external validation. The area under the receiver operating characteristic curve (AUC) value is a measure for the discriminative ability of a prediction model, ranging from 0.5 (flipping a coin) to 1.0 (perfect discrimination). For the Erasmus Guillain–Barré Syndrome Respiratory Insufficiency Score (EGRIS), this represents the ability of the model to distinguish between patients who need and do not need mechanical ventilation. The external (Ext.) validation AUC = the discriminative ability of the original EGRIS model in the International Guillain–Barré Syndrome Outcome Study (IGOS) cohort. Refitted AUC = the discriminative ability of the model after refitting, in other words, re‐estimation of the odds ratio based on the IGOS data. The refitted AUC provides the optimum discriminative ability that can be obtained with these 3 clinical factors in the IGOS dataset. The dotted line represents the AUC value in the EGRIS development cohort. CI = confidence interval; Eu/NA = Europe/North America.

FIGURE 3

Observed probabilities versus predicted risks. Mean observed proportions of mechanical ventilation (MV) within 1 week in the International Guillain–Barré Syndrome Outcome Study validation cohorts versus predicted risks based on the Erasmus Guillain–Barré Syndrome Respiratory Insufficiency Score model are shown. Eu/NA = Europe/North America.

FIGURE 4

Calibration curves: original and after recalibration. This figure provides the calibration curves for the original (left) and recalibrated (right) Erasmus Guillain–Barré Syndrome Respiratory Insufficiency Score (EGRIS) model, for the full International Guillain–Barré Syndrome Outcome Study cohort, Europe/North America (Europe/North America), and Asia. Observed probabilities of mechanical ventilation (y‐axis) are plotted against predicted risks based on the EGRIS model (x‐axis). The dotted lines represent perfect calibration (ie, predicted risks are equal to observed frequencies). The gray‐shaded areas are 95% confidence intervals around the calibration curves. NA = not applicable.

FIGURE 5

Predicted probabilities of mechanical ventilation within 1 week according to the recalibrated Erasmus Guillain–Barré Syndrome Respiratory Insufficiency Score (EGRIS) Europe/North America (Eu/NA) model. This figure provides the predicted probabilities of the need for mechanical ventilation within the first week from hospital admission based on the EGRIS (scores 0–7). Probability graphs are based on the original EGRIS model (red line) and the recalibrated model for the Eu/NA subgroup (EGRIS‐Eu/NA; green line). Dashed and gray areas around the curves represent the 95% confidence intervals. The EGRIS model can be applied to all patients with Guillain–Barré syndrome (GBS), including mild cases (GBS disability score ≤ 2) and GBS variants. The EGRIS total score can be calculated based on the scoring system provided in Table 1. With the EGRIS total score and the probability graphs provided above, one can deduce the predicted probability of the need for mechanical ventilation for an individual patient with GBS. To predict the need for mechanical ventilation within the first week in Eu/NA GBS patients, the probability graph based on the recalibrated model can be used: EGRIS‐Eu/NA (green line). For predictions in GBS patients from countries outside Europe: North America, the probability graph based on the original validated EGRIS model can be used (red line). EGRIS = Erasmus Guillain–Barré Syndrome Respiratory Insufficiency Score; MV = mechanical ventilation.