Predicting weight using postmenstrual age – neonates to adults

Abstract

Summary Objectives: To describe the pattern and variability of body weight with postmenstrual age (PMA) using nonlinear mixed effect modeling and to create a single mathematical function that can be used from prematurity to adulthood. Background: PMA has been shown to predict functional properties of humans such as glomerular filtration rate and drug clearance. Widely used growth charts use postnatal age to predict weight in an idealized population and are not available as a mathematical function. Methods: We modeled 7164 body weight and PMA observations from a pooled database of 5031 premature neonates, infants, children, and adults. All subjects were participants in pharmacokinetic or renal function studies. PMA ranged from 23 weeks to 82 years. A mixed effect model was used to describe fixed (PMA, sex) and random between‐subject variability. Results: A model based on the sum of three sigmoid hyperbolic and one exponential functions described the data. Females were typically 12% lighter in weight. Part of the between‐subject variability in weight decreased exponentially with a half‐life of 3.5 PMA years, while the remainder stayed a constant fraction of the weight asymptote for each of the four functions. Conclusions: The change of weight with PMA and sex can be described with a simple equation. This is suitable for simulation of typical weight–age distributions and may be useful for evaluation of appropriate weight for age in children requiring medical treatment.

Predicting Pediatric Age-Matched Weight and Body Mass Index

“…Sumpter and Holford previously used a Hill-type function to describe body weight and postmenstrual age relationship in premature neonates, infants, children, and adults (15). However, with this approach using the CDC and WHO datasets and adding 9 months to adjust from postnatal age to postmenstrual age, their equation did not quite capture the overall variability of the CDC dataset (Fig.…”

“…1 of Sumpter and Holford (15) was used to simulate 10,000 age-matched weights in pediatric population (gestational age between 0 and 18 years). The interindividual variability was characterized by an exponential model.…”

“…The model-predicted age-matched data and the percentiles from the two agencies were compared using the chi-squared test . The fitting and evaluation algorithms and the 10,000 simulations to determine the 95% prediction intervals including the simulations based on equations from Sumpter and Holford (15) were done in R 3.1.0.…”

“…The resulting weights often do not reflect the true age-weight relationship in the pediatric population. Sumpter and Holford previously developed a Hill-type equation to describe the relationship between weight and postmenstrual age from neonates to adults (15). Their model was rather quite complex, and its application in pharmaceutical Electronic supplementary material The online version of this article (doi:10.1208/s12248-014-9657-9) contains supplementary material, which is available to authorized users.…”

Relationship between body weight and postmenstrual age in a Korean pediatric population

“…However, the problem with using post-natal age has been raised in that post-natal age is less likely to reflect a continuous growth process in the pediatric population, particularly in pre-term to infant babies, and less likely to correlate with PK parameters than using post-menstrual age. [6,7] Hence, there are suggestions of using PMA instead of post-natal age when growth or organ maturation is considered. In line with this suggestion, PMA was used in our analysis, which demonstrated that average weights of new born babies were different for different PMA groups despite being in the same postnatal age group.…”