RESUMEN
Testosterone (T), sex hormone binding globulin (SHBG), free testosterone (FT) and bioavailable testosterone (BAT) are commonly employed tests in pediatric endocrinology and all require age-dependent reference intervals for interpretation. The common methods used to derive these reference intervals require decisions about data shape and/or age partition thresholds, which can result in sharp differences between age groups, particularly for pubescent children. Partitioning also results in a form of data loss, where data from one age-bin is completed disconnected from the adjacent age-bins. Non-parametric continuous reference intervals methods have previously been developed to avoid some of these drawbacks. These strategies use all the available data and smooth transitions between ages avoiding partitioning. However, the fitting process involves selection and adjustment of many parameters and it can be difficult to maintain a reproducible approach. Here we provide a workflow for non-parametric continuous reference intervals applied to T, FT, BAT, and SHBG using the R language quantregGrowth package. T measurements were determined by LC-MS/MS, FT and BAT were calculated, and SHBG was measured on the Roche Cobas e601. The continuous interval methodology is described in detail with code examples and illustrations for reproducibility.
RESUMEN
BACKGROUND: The monitoring of head circumference (HC) is essential to early detect any conditions affecting its growth in early childhood. A positive secular trend and regional specificities in HC suggested the need to provide updated national HC reference growth charts. METHODS: We extracted all growth data collected from 42 primary-care physicians from across the French metropolitan territory who used the same electronic medical-records software. We selected HC measurements up to age five years for all children who were born after 1990 with birth weight > 2500 g. We derived new HC growth charts by using Generalized Additive Models for Location, Scale and Shape, then externally validated them until 30 months of age by comparison with the national population-based Étude Longitudinale Française depuis l'Enfance (ELFE) birth cohort and compared them to previous French and WHO growth charts. FINDINGS: With 973,869 HC measurements from 157,762 children, new calibrated HC growth charts from birth to age five years were generated. The new HC growth charts showed good external fit by comparison with the ELFE birth cohort. As compared with the new HC growth charts, the previous French and WHO growth charts mean HC z-scores were, respectively, -0.4 and -0.6 SD for girls and -0.2 and -0.6 SD for boys. INTERPRETATION: We produced and validated national calibrated HC growth charts by using a novel big-data approach applied to data routinely collected in clinical practice. Comparison with previous French and WHO growth charts confirmed a positive secular trend since the 1960s and regional specificities. FUNDING: The French Ministry of Health; Laboratoires Guigoz-General Pediatrics section of the French Society of Pediatrics-Paediatric Epidemiological Research Group; the French Association of Ambulatory Pediatrics; and educational grant from the Regional Health Agency of Ile-de-France.
RESUMEN
BACKGROUND AND OBJECTIVE: This study aimed to establish reference equations for spirometry in healthy Taiwanese children and assess the applicability of the Global Lung Function Initiative (GLI)-2012 equations to Taiwanese children. METHODS: Spirometric data collected from 757 healthy Taiwanese children aged 5 to 18 years in a population-based cohort study. Prediction equations derived using linear regression and the generalized additive models for location, scale and shape (GAMLSS) method, respectively. RESULTS: The GLI-2012 South East Asian equations did not provide a close fit with mean ± standard error z-scores of -0.679 ± 0.030 (FVC), -0.186 ± 0.044 (FEV1), -0.875 ± 0.049 (FEV1/FVC ratio) and -2.189 ± 0.063 (FEF25-75) for girls; and 0.238 ± 0.059, -0.061 ± 0.053, -0.513 ± 0.059 and -1.896 ± 0.077 for boys. The proposed GAMLSS models took age, height, and weight into account. GAMLSS models for boys and girls captured the characteristics of spirometric data in the study population closely in contrast to the linear regression models and the GLI-2012 equations. CONCLUSION: This study provides up-to-date reference values for spirometry using GAMLSS modeling in healthy Taiwanese children aged 5 to 18 years. Our study provides evidence that the GLI-2012 reference equations are not properly matched to spirometric data in a contemporary Taiwanese child population, indicating the urgent need for an update of GLI reference values by inclusion of more data of non-Caucasian decent.