Human growth is a dynamic process that needs careful documentation. It is recommended to refer individual growth to a reference population, and to transform and plot individual measurements into percentiles or standard deviation score (SDS) scales. A certain amount of percentile or SDS crossing is a physiological phenomenon that occurs at all ages and relates to the individual changes in developmental tempo. Between early childhood and adulthood, two thirds of all children and adolescents cross >1 SD in height. Particularly during pubertal age, SDS crossings can lead to several characteristic patterns such as sharp downward or upward SDS peaks. Upward SDS peaks indicate faster than average tempo, downward SDS peaks indicate slower than average tempo. Almost half of the pubertal height variation consists of variation in tempo. Applying functional data analysis and principal component analysis, the two main sources of height variance, i.e. tempo and amplitude, can be statistically separated and quantified. This review aims to renew some of the old debates on how to assess growth, and to facilitate forthcoming consensus upon how to appropriately evaluate height and changes in height at brief and clinically relevant intervals.
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