Transl Clin Pharmacol.  2017 Jun;25(2):101-105. 10.12793/tcp.2017.25.2.101.

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

• Guk J
• Chae D
• Park K

• KMID: 2386767
• DOI: http://doi.org/10.12793/tcp.2017.25.2.101

Abstract

Weight is a covariate representative of body size and is known to influence drug disposition. Recently, with increased use of allometric scaling, this variable has become more significant in accounting for variability in pharmacokinetic parameters. In adults, weight can be considered as a time invariant covariate because physical development is complete. As a result, when weight is missing in data, the typical or median value (say, 70 kg) could be imputed. On the contrary, weight continuously changes with age in the pediatric population. In this case, it is more appropriate to consider different median weight for each age group. We constructed a prediction model for weight using postmenstrual age (PMA) with the data consisting of 83,014 Korean pediatric patients. Weight, PMA, and gender information were collected from electronic medical records. Sigmoid models multiplied by exponential or logistic function were tested for basic model structure. Covariate effects on model parameters were then investigated using selection criteria of p < 0.001. All analyses were performed using NONMEM 7.3.0 and R3.2.0. The sigmoid model multiplied by logistic function best described the data and there was a significant difference between boys and girls in model parameters. It is expected that the results obtained in this work can be used for imputation of missing weights in pediatrics when PMA is available. In addition, the developed model can be used for clinical studies in children under 12 years old whose weight change rapidly with age and for model building in dealing with time varying body weight as a covariate.

Keyword

Body weight; Prediction model; Pediatric population; Postmenstrual age

MeSH Terms

Adult
Body Size
Body Weight*
Child
Colon, Sigmoid
Electronic Health Records
Female
Humans
Patient Selection
Pediatrics
Weights and Measures

Figure

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  Figure 1 Raw data (postmenstrual age (weeks) (PMA) versus weight). Grey dots and black solid lines stands for observations and smoother lines of observations, respectively.

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  Figure 2 Goodness of fit plots. DV, PRED, and PMA means a dependent variable (weight), predicted weight, and postmenstrual age (weeks). Grey dots stand for observations, dotted lines are line of identity (DV vs PRED) and line of zero residual value (CWRES vs PMA and CWRES vs PRED). In the Body weight vs PMA plot, dotted line is smooth of observation and solid line is model prediction.

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  Figure 3 Goodness of fit plot of each subgroup(Upper : neonate to infant, lower : child). Dots are observations, dotted lines 25%, median and 75% percentiles of observations, and solid lines 25%, median and 75% percentiles of predictions.

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  Figure 4 Difference of weight between boys and girls. Dots are observations and solid line and dashed line denotes median predictions for boys and girls, separately.

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