ABSTRACT
Background
Z scores are the method of choice to report dimensions in pediatric echocardiography.
Z scores based on body surface area (BSA) have been shown to cause systematic biases
in overweight and obese children. Using aortic valve (AoV) diameters as a paradigm,
the aims of this study were to assess the magnitude of z score underestimation in children with increased body mass index z score (BMI-z) and to determine if a predicting model with height and weight as independent predictors
would minimise this bias.
Methods
In this multicentre, retrospective, cross-sectional study, 15,006 normal echocardiograms
in healthy children 1-18 years old were analyzed. Residual associations with body
size were assessed for previously published z score. BSA-based and alternate prediction models based on height and weight were
developed and validated in separate training and validation samples.
Results
Existing BSA-based z scores incompletely adjusted for weight, BSA, and BMI-z and led to an underestimation of > 0.8 z score units in subjects with higher BMI-z compared with lean subjects. BSA-based models led to overestimation of predicted
AoV diameters with increasing weight or BMI-z. Models using height and weight as independent predictors improved adjustment with
body size, including in children with higher BMI-z.
Conclusions
BSA-based models result in underestimation of z scores in patients with high BMI-z. Prediction models using height and weight as independent predictors minimise residual
associations with body size and generate well fitted predicted values that could apply
to all children, including those with low or high BMI-z.
RÉSUMÉ
Contexte
Les scores z sont la méthode de choix pour rapporter les mesures faites à l’échocardiographie
pédiatrique. Il a été montré que les scores z basés sur la surface corporelle étaient associés à des biais systématiques chez les
enfants en surpoids et obèses. En utilisant comme paradigme le diamètre de la valve
aortique, les auteurs de cette étude ont voulu évaluer l'ampleur de la sous-estimation
des scores z chez les enfants avec un score z de l'indice de masse corporelle (IMC-z) élevé, et déterminer si un modèle prédictif utilisant la taille et le poids comme
variables prédictives indépendantes pouvait minimiser ce biais.
Méthodologie
Dans cette étude transversale, rétrospective et multicentrique, 15 006 échocardiogrammes
normaux d'enfants en bonne santé et âgés de 1 à 18 ans ont été analysés. Les associations
résiduelles avec la taille corporelle ont été évaluées par rapport aux scores z déjà publiés. Des modèles basés sur la surface corporelle et d'autres modèles basés
sur la taille et le poids ont été conçus et validés à l'aide d'échantillons d'apprentissage
et de validation distincts.
Résultats
Les scores z existants basés sur la surface corporelle ne permettent qu'un ajustement partiel
du poids, de la surface corporelle et de l'IMC-z, et ont entraîné une sous-estimation de plus de 0,8 unité du score z chez les sujets dont l'IMC-z est élevés, comparativement aux sujets sans surpoids. Les modèles basés sur la surface
corporelle ont entraîné une surestimation des diamètres prédits de la valve aortique
lorsque les valeurs du poids ou de l'IMC-z augmentaient. Des modèles utilisant la taille et le poids comme facteurs prédictifs
indépendants ont permis d'améliorer l'ajustement en fonction de la taille corporelle,
y compris chez les enfants dont l'IMC-z est plus élevé.
Conclusions
Les modèles basés sur la surface corporelle entraînent une sous-estimation des scores
z chez les patients dont l'IMC-z est élevé. Les modèles prédictifs utilisant la taille et le poids comme facteurs
prédictifs indépendants permettent de minimiser les associations résiduelles avec
la taille corporelle, et produisent des valeurs prédites mieux ajustées pouvant être
appliquées à tous les enfants, y compris ceux dont l'IMC-z est faible ou élevé.
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Article info
Publication history
Published online: June 30, 2021
Accepted:
June 24,
2021
Received:
April 27,
2021
Footnotes
See page 1796 for disclosure information.
Identification
Copyright
© 2021 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.
