Reference intervals for iron-related blood parameters: results from a population-based cohort study (LIFE Child)

Abstract

Background: Pediatric reference intervals for iron-related parameters are determined continuously over time from a highly standardized sample collection by application of the R-package generalized additive models for location, scale and shape (GAMLSS), which is little known in laboratory medicine. Methods: Two thousand seven hundred and seventy-eight samples from Leipzig research center for civilization diseases (LIFE) Child participants at the age of 2.5-19 years were analyzed on a Sysmex XN-9000 for hemoglobin and reticulocytes and on a Roche Cobas 8000 for transferrin and ferritin. Reference intervals were established by repeated model calculation by use of the LMS (λ-μ-σ) method from Cole with specifically weighted subsamples. Results: Continuous and gender-specific reference intervals as well as smoothed percentile curves were

Reference curves for refraction in a German cohort of healthy children and adolescents

“…For statistical analysis, the software R, by the R foundation, with the additional package "gamlss" was used. This method has been used in former papers analysing the LIFE Child database in order to create reference curves [20,21]. While the LMS distribution is the most commonly used with this method [2] it does not allow modelling of negative values, which are present in the spherical equivalent.…”

Does physiological distribution of blood parameters in children depend on socioeconomic status? Results of a German cross-sectional study

“…Interpreting the results in terms of z-scores is in accordance to the recommendations of WHO 28 34 and has several advantages: z-scores have the same statistical relation to the distribution of the reference around the mean at all ages, which makes results comparable across age groups, are directly related to percentiles and yield a better representation of physiological processes. 35 36 …”

“…34 Detailed information of this complex resampling technique has been described in previous studies. 35 36 Raw WSI and its dimensions considered as metric scales.…”

New pediatric percentiles of liver enzyme serum levels (alanine aminotransferase, aspartate aminotransferase, γ‐glutamyltransferase): Effects of age, sex, body mass index, and pubertal stage

“…These may be interpreted as relating to location (median), scale (centile‐based coefficient of variation), skewness (power transformation to symmetry), and kurtosis (degrees of freedom) . Estimation of parameters as continuous functions of age seems to be a more appropriate approach to reflect the physiological development of laboratory analytes …”

“…(20) Estimation of parameters as continuous functions of age seems to be a more appropriate approach to reflect the physiological development of laboratory analytes. (9,21) Because LIFE Child has a longitudinal study design and recruits families participated with more than one child, our sampled data contain multiple measurements per child as well as measurements of siblings. Therefore, percentile calculations had to follow an adapted approach.…”