120 Chapter 6 updated. All images were analyzed by one radiologist. Images with excessive movement artifacts were excluded at the judgement of the radiologist. Potential confounders The following factors are known to relate to body composition and were assessed as potential confounders: gestational age, gender, ethnicity, type of nutrition : human milk (60% or more of total diet) vs formula (60% or more of total diet), waist circumference and absolute weight, length and head circumference at birth and term age and their corresponding z-scores (15). The statistical analysis Characteristics of the study group were first summarized using descriptive statistics, stratified by sex. Mean and standard deviations (SD) were calculated for all continuous variables and presented as mean + SD. Percentages were reported for dichotomous variables. The median and the interquartile range were reported if the variable was not normally distributed. The level of agreement and potential bias between fat mass percentage obtained via ADP and DXA was examined using the Bland-Altman analysis (12). Agreement between the formula of Schmelzle et al (12). and fat mass was also examined using Bland Altman plots. Based on the normal variation in fat mass the maximum allowed difference was set at 200 g for absolute fat mass and at 2% for fat mass percentage (21-23). Prediction models were developed for the predicting variable ∑SFT and absolute fat mass and fat mass percentage measured with ADP at term equivalent age. Potential confounders which showed significant correlations with fat mass (percentage) in univariate analysis were added together in a multivariate model. The final model was determined through a backward stepwise regression analysis. The removal criterion was: F-to-remove > 0.10. All statistical analyses were conducted using IBM® SPSS® Statistics 22 for Windows (IBM Corp., Armonk, NY, USA). Two-sided statistical significance was assumed at p-values less than 0.05 with a 95% confidence interval. Results Sixty-five infants were assessed for growth and body composition at term age. Baseline characteristics are shown in table 1. Measurements of skinfolds were successfully completed in 63 infants, ADP was successful in 58 infants and DXA in 32 infants (see figure 1).
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