Stage line diagram: An age‐conditional reference diagram for tracking development

Abstract

This paper presents a method for calculating stage line diagrams, a novel type of reference diagram useful for tracking developmental processes over time. Potential fields of applications include: dentistry (tooth eruption), oncology (tumor grading, cancer staging), virology (HIV infection and disease staging), psychology (stages of cognitive development), human development (pubertal stages) and chronic diseases (stages of dementia). Transition probabilities between successive stages are modeled as smoothly varying functions of age. Age-conditional references are calculated from the modeled probabilities by the mid-P value. It is possible to eliminate the influence of age by calculating standard deviation scores (SDS). The method is applied to the empirical data to produce reference charts on secondary sexual maturation. The mean of the empirical SDS in the reference population is close to zero, whereas the variance depends on age. The stage line diagram provides quick insight into both status (in SDS) and tempo (in SDS/year) of development of an individual child. Other measures (e.g. height SDS, body mass index SDS) from the same child can be added to the chart. Diagrams for sexual maturation are available as a web application at http://vps.stefvanbuuren.nl/puberty. The stage line diagram expresses status and tempo of discrete changes on a continuous scale. Wider application of these measures scores opens up new analytic possibilities.

European Consensus Statement on congenital hypogonadotropic hypogonadism—pathogenesis, diagnosis and treatment

“…90 In addition, use of the stage-line diagram enables the identification of patients with delayed puberty, which is based not only on pubertal onset but also on the tempo of pubertal development. 91 In most of these individuals, puberty is initiated and eventually completed (that is, constitutional delay of growth and puberty [CDGP]). By contrast, adolescents with CHH lack pubertal activation of the HPG axis, which leads to absent puberty and infertility ( Figure 1).…”

“…[92][93][94] Adolescents with CHH exhibit steady linear growth and thus lack the so-called growth spurt. 91,95,96 Given the delayed epiphyseal closure, these individuals often have eunuchoidal proportions. The most common complaints in male adolescents with CHH include absent and/or minimal viriliza tion, low libido and lack of sexual function.…”

“…135 A stage-line diagram is useful for providing developmental stages ±SD or as percentiles, as well as the tempo of pubertal development ±SD per year. 91 Additionally, signs of associated developmental anomalies such as cryptorchidism with or without micropenis, midline defects or signs suggestive of combined pituitary hormone deficiency should be evaluated (Box 2).…”

Growth charts of human development

“…The standard deviation is smaller than 1, due to rounding, floor and ceiling effects. 47 The user places a mark on the stage line corresponding to the observed stage at the child's age, and connects the mark to the previous measurement. A move to the next stage produces a jump in the curve.…”

Recent advances in the understanding and management of delayed puberty

“…Longitudinal assessments are important as pubertal arrest is particularly significant. The use of stage-line diagrams (puberty nomograms) aids the identification of pubertal delay or arrest delay based on the onset as well as tempo of pubertal development 36. Baseline investigations, if indicated to exclude underlying diseases, are guided by the clinical assessment.…”