1. Overview. Wei and He are to be congratulated on an innovative and important article. The conditional approach to growth charts described in their article is important in a practical sense, and the use of quantile regression is both natural and well motivated. We look forward to further application of their idea to actual practice, because the concept of “falling behind” in one’s growth cycle...

First, I would like to congratulate the authors for an interesting application of their semiparametric quantile regression model to longitudinal human growth data. On an earlier occasion, I had an opportunity to collaborate with the authors on applying this method for the purpose of constructing semilongitudinal growth charts for height and for body mass index. As my background is in medicine r...

Estimation of reference growth curves for children's height and weight has traditionally relied on normal theory to construct families of quantile curves based on samples from the reference population. Age-specific parametric transformation has been used to significantly broaden the applicability of these normal theory methods. Non-parametric quantile regression methods offer a complementary st...

BACKGROUND AND OBJECTIVES Children with Down syndrome (DS) have lower birth weights and grow more slowly than children without DS. Advances in and increased access to medical care have improved the health and well-being of individuals with DS; however, it is unknown whether their growth has also improved. Our objective was to develop new growth charts for children with DS and compare them to ol...

Many congenital diseases are associated with growth failure, and patients with these diseases have specific growth patterns. As the growth patterns of affected individuals differ from those of normal populations, it is challenging to detect additional conditions that can influence growth using standard growth charts. Disease-specific growth charts are thus very useful tools and can be helpful f...

First of all, we would like to thank all the discussants for their encouragement of and insightful comments on our work. We are especially appreciative of their unique perspectives brought to the topic of conditional growth charts. The discussants raised a number of interesting questions from statistical as well as clinical points of view, some of which are broader and deeper than what we will ...

BACKGROUND Growth charts based on data collected in different populations and time periods are key tools to assess children's linear growth. We analyzed the impact of geographic factors and the secular trend on height-for-age charts currently used in European populations, developed up-to-date European growth charts, and studied the effect of using different charts in a sample of growth retarded...